@Background Pony #3715  
That’s actual a pretty accurate way how a flamethrower actually works, which is by spraying a flammable liquid.
 

 
And it’ll be interesting to see if that character ever shows up again “crisped” or if he actually is completely burned to death (IE: he never shows up in another scene).

rip  

@DashVader  
Usually for joke effect, hence the “zippo spike” tag we use.

@Daneasaur  
For one thing, earlier in the movie when Twilight got kidnapped, he definitely set the guard on fire himself that time. Besides, I’m fairly certain he’s controlling the fire himself in this sequence. We’ve seen other characters induce his fire breath before, in particular Applejack in season three, and it didn’t look anything like what Capper’s doing here.

@DashVader  
Him or capper?
 
Spike is a prop in this sequence.

I’m pretty sure Spike is the first character to intentionally (and apparently, SUCCESSFULLY) use lethal force onscreen.

@Background Pony #8D18  
We can also excuse it as part of his pony upbringing to have curbed his fire usage, which Ember showcased is so second nature to normal dragons, nothing flammable exists in the dragon lands.
 
Much like the knowledge of using a hammer. It can be used in proper settings (pound a nail, break a rock) and be useful, but can most often be destructive if used in any other setting, and if someone was born for hammers with hands, they would need to be taught to be gentle with everything to the point that using their hands as weapons never comes across as a viable idea.
 
But on the flipside when all hope is lost and they are reminded that they need to fight and use said hammer hands? That they no longer have to hold back?
 
I think that paints a proper picture.
 

@Background Pony Number 17  
If he really had no qualms about it, he’d use it much more often as a weapon. It would’ve saved him and his friends many times.  
We know he can easily produce huge blasts of fire when he wants (Equestria Games) and make it hot enough to melt metal in a second (Inspiration Manifestation). Like some have said though, his upbringing by ponies seems to have made it harder for him to do it when he’s afraid.
 
Don’t know about the movie, but him being so casual about letting someone use him to fry some people is actually out of character. Timberwolves, Diamond Dogs, Changelings, etc. How many times could this ability have saved them, yet he never wants to use it.
 
Though I guess you could chalk it up to the writers simply not wanting him to be the hero. The argument that a kid’s show wouldn’t show creatures being burned alive isn’t that strong because just like in his knight dream (Dog and Pony Show) they could just make it so the fire barely reaches the villians before they run away in terror.

U.S Marine stands up from his foxhole to engage oncoming Japanese soldiers (Okinawa 1945, colorized)

@Background Pony Number 17  
“Spike got an idea. An awful idea. Spike got a wonderful, awful idea.”  

@Background Pony #DC82  

 
Actually, it was “Spike kills the G-rating.” Capper asks Spike if he’s a fire-breathing dragon, and the grin on Spike’s face is terrifying to behold. Turns out the little guy has no qualms about using his fire breath on folks after all.

That flame was a nut hair away from my skin!!

@thps48  
That’s basically it. Ember showcased that Dragons might even be “allergic” to expressing their feelings, resulting in her sneezing explosive blasts of fire, possibly as a sort of overload.
 
When Spike is joyful, he can use his fire with no issues and can use it pretty potently if he’s angry (he nearly took RD’s head off in Over a Barrel, when she wanted him to pop the last few popcorn kernels). The only times he “can’t” use his fire very well is when he’s afraid, which was both in Equ games and Dragon quest, resulting in little more than whispy sparks coming from his mouth.
 
The lighter joke was just for effect.

@thps48  
You know that actually makes sense. We have already seen what greed can do to a dragon so emotions may have a major impact here.

@FlonnesIkramant  
It could depend on his confidence level, maybe. Ember and all other dragons don’t appear to have as much trouble in the department because they don’t take consideration of feelings as often, unlike Spike whose emotions are always exposed due to living with ponies all his life. :3

@Daneasaur  
I think it’s more about the magnitude of the fire breath when he’s being used versus doing it by himself. Maybe flame control wasn’t the right way to word it since he can use it whenever (although he may lose control from time to time). We haven’t really seen enough of spike being used to determine whether the user has more control. Maybe if spike was picked up like this at the games he could have used his breath no problem.

@Background Pony #B86B
 
@justanotherponi  
Are we even watching the same show?
 
Spike can freely use his fire whenever he wants.
 

 

 
In fact, his only issue is not using his fire when he exhales occasionally.
 

 

@Background Pony #B86B  
It isn’t, he can use his fire on demand. The only time he “couldn’t” was in equestria games, which we don’t talk about.

Pyro’s new weapon

@Background Pony #B86B  
I mean, there was that one time in the Crystal Empire Equestria Games…

@Background Pony #B86B
 
There are 2 possible explainations:
 

Why is Spike’s flame control so weak unless he’s someone’s zippo. That kind of fire could have come in handy for him so many times.

Spike is best flamethrower

Spike learned this from Twilight: