@CURRENT YEAR GUY
 
You’re kind of leaving out how that would also mean that:
 
-Crop production would decrease significantly without earth pony magic  
-And decrease even further without weather control  
-The day and night cycles also being left uncontrolled would also open a lot of variables on that front, and none of them good. And there would be no easy way out of that with something like Twilight’s amulet because all the amulets would be useless too.
 
All this adds up to mass starvation and death while the ensuing chaos would weaken Equestria even further and open it to attacks by the same non-ponies she just alienated.
 
At best, that was a horrendously poorly-thought-out plan, Great Leap Forward-style.
 
At worst, she already expected these consequences to happen and they were her entire goal.
 
She might have been banking on that chaos to assume supreme power, but even that was equally poorly-planned, because there’s no way a little filly, as manipulative as she is, would keep a situation of the sort within her control for too long.
 
And seriously, democracy on a nation where the average pony pretty much changes all of their opinions based on who they heard last without any regards to credibility is doomed from the start.

@Background Pony #088A  
So basically you can sum up your argument as:  
>But Cozy was Evil!  
>And the rest of them are useful, cozy glow is a useless pony!!!  
>Why should we keep useless evil fillies alive when we have Back stabbing chimeras, literal love stealing bug queens and magic eating centaurs that want to destroy everything, that make so much more sense to keep alive?
 
Also no, there is no proof that Cozy Glow is a psychopath, we’ve seen so little of her and absolutely nothing about her backstory to make such a presumption.  
“WOW GOSH, see how evil that little pony is when she attempts to suck all the magic out of Equestria?”  
“Clearly she must be a psychopath, there’s no way someone can do such evil things in on the way to their ambition in ruling Equestria with friendship”.  
“She must be completely unable to feel empathy for her to be doing such EVIL things.”
 
Yeah, nah, not to mention Cozy Glow and Tirek were actually feeling friendship back on Mount Everhoof before Chrysalis stopped them. If such a thing occurred it would only makes sense that Cozy Glow is capable of friendship, and by extension empathy.
 
Also shes not a terrorist, at most shes a revolutionary trying to overthrow the tyrannical upper class nobility and their monarchy. Have you noticed that once she removed magic from equestria, every pony would be on equal foot, there wouldn’t be any alicorns to rule and unicorns would lose the absolute advantage they have over the other tribes? Cozy Glow is a pony who saw the system for what it is, a government ruled by the most magical ponies and that she would unable to advance any higher in the government due to being a pegasus. At most all she can do is hope to marry into royal blood.  
But if she removed the unicorns magic, Alicorns would be a thing of the past and all ponies would be forced to be on equal foot. Her ambition to rule is plain as day, but her actions would have resulted in an equal equestria. As for why she attempted to eliminate the Mane 6 and spread hatred of non-ponies is quite simple. Draining all the magic from equestria would leave Equestria temporary weakened, so deporting all those dangerous non-ponies is a must until some manner of control comes back into equestria though the power of democracy. She attempted to kill the Mane 6 because in her eyes they were traitors, they were lower class ponies helping an alicorn collect power through politics so they can become powerful themselves. Suffice to say, they call this “friendship”, and its utterly corrupt.  
Friendship, when it comes down to it, is ultimately power in equestria.

@Background Pony #088A
 
I’ll have to disagree on those last two:
 
Not only Tirek would pretty much only use the magic he acquired to kill as much stuff as he could if he won (as we saw in The Cutie Re-Mark), it probably has been so long since he first came there that whatever land he came from wouldn’t want anything to do with him - he’d be just some renegade that just happens to be very distantly related to the king - it’s very unlikely that his parents would be immortal.
 
And Chrysalis is not that different from Cozy either.

@CURRENT YEAR GUY  
That sound perfect if we talk about a normal pony  
Starlight is a normal pony  
Cozyglow is a psychopath and you can’t negotiate with psychopaths.
 
Starlight Glimmer is actually useful for the future of equestria, she and sunburst make literally a second starswirl to help equestria  
Discord can solve any problem with his magic if everything turn really dangerous for the mane 6  
Queen Chrysalis would be a good queen if she regain her love for her hive and collaborate with equestria  
Tirek only have problem with his parent but he is still royalty in another kingdom and would help the relation between equestria and king vorax empire  
Meanwhile with Cozyglow you only have a really dangerous psychopath pegasus that her only function will be put equestria in danger everytime she is free.  
To be honest cozy don’t even deserve the petrification, she deserve the same fate of king sombra. Why we should keep a really dangerous terrorist alive? Just to ruin the life of ponies and non ponies(and ruin years of ponies trying accept the non ponies to their country)?

@Background Pony #70FB  

 
Cute, but if we’re talking about chances of redemption, she received none. Not to mention “chances to turn herself around” can mean literally anything. Starlight had a chance of turning her life around after running away from the village, starlight had a chance to turn her life around while making her plan to literally destroy the lives of the Mane 6 by fucking around with time and space. Starlight had a chance to turn her life around and try and make up with Starburst and not pursue the goal of communism. The difference between Cozy Glow and Starlight is that Twilight couldn’t beat Starlight so she had to resort to dragging her into the future, which was desolate of life. And even then Twilight still had to keep talking to her to convince her that this was a bad idea.
 
But Cozy Glow could be beaten, she was beaten by literal children first time round and the second time she was de-alicorned and outnumbered, both times she wasn’t offered redemption once. Cozy Glow is still a filly, she had lost her magic and could be kept in a cage. She didn’t need to be Petrified.
 
Unless of course Discord broke her out again, one of the long list of betrayals again the Mane 6 that he has committed, and forgiven every time.

Here’s the thing about Cozy Glow: She was given every possible chance to turn herself around and she threw it all away. She was a student at Twilight’s school. She was in a caring and supportive environment, surrounded by responsible and understanding adults and children her own age who all genuinely wanted to be her friend. She was personally tutored on the values of friendship by the CMC and by Starlight. She had every chance in the world and she deliberately turned her back on every one of them.

@Background Pony #86FA  
So did Nightmare Moon and Starlight.

She tried killing the Mane 6. Enough said.

Indeed! She may been evil but she was the ONLY villian, who they never gave a second chance, neither tried to find out her reasons.

@Mildgyth  
Didn’t Starlight also escape the first time she was beaten? In fact, Twilight let her escape after having to defend three ponies from her attack.
 
And I don’t think learning stuff like history and animal care while seemingly never taking part in any extracurricular activities would have changed her already preconcieved notions of friendship before coming to the school.

@Background Pony #BCE4
 
Kind of hard to give her that when the first thing she does after that is try to escape.
 
And frankly, given that she already had been in a School of Friendship for a few months, already studying under Twilight and the only things she learned from it were how to manipulate ponies and personal information that she could use against them, and her only regret was that she got caught, trying to reform her with their normal means would pretty much fall under Narcotics Anonymous’ definition of insanity unless they resorted to whetever reforming spell Twilight was researching when Discord was unpetrified, but people wouldn’t consider the latter any better than what we got…

@Background Pony #EAAB
 
She never offered her anything, only asked why she did it. She never offered her any second chances.

@Background Pony #BCE4  
That’s not necessarily true. Before she was sent to Tartarus, Twilight did reach out to her and gave her a moment to make a choice….and she made it.

She really wasn’t given a chance. Not like Starlight, Discord and Luna. Why were those three given a second chance and not her? Kind of a double standered going on there.

@Hericks
 
Yeah, Cozy. It appears that not that many people still forgive you for many of the actions you committed. :P

“All I did was try to torture and commit mass murder! Oh yeah, and treason… and destroy all magic which would leave ponies completely defenseless and most likely cause genocide of all creatures in Equestria. Is that so bad?”

@Background Pony #2DCD  
Hnnnggg!

@Somber Star
 
I have realized that and yes that is indeed a wrong thing to do. xD I am not forgetting all the terrible things that this filly has done. :P I’m more mixed on this whole thing. x3

Yes, you did. You should be thanking Ahriman that this is a jam you still can get out of somehow.
 
Like they say, don’t do the crime if you can’t do the time.

@OP You do realize that she tried to destroy all magic in Equestria, which would have completely annihilated the ponies’ way of life, at the start of her criminal career, right? Also, she’s totally unrepentant.

@Background Pony #2DCD
 
That image is always adorable. xDD