Though we haven’t seen much of the Pegasus culture, my guess is that they still have a spartan-esque, militaristic culture. Though Equestria has enjoyed a long era of relative peace between the two Lunar Rebellions, there are still dangers that could necessitate militarisitic action, just on a smaller scale. Also parts of their culture have most likely adapted to the peaceful times. The Wonderbolts were more than likely the elite squads for the Pegasus forces, similar to the Navy Seals for the U.S. Navy. As seen in “Secret of My Excess,” they still can perform as an elite fighting team (though it seems they don’t have much practice against dragons in that regard). Also the most commonly seen Royal Guards are Pegasi. There are other practical reasons for that, but it also can tie into the pegasi’s culture and traditions.  
The harsher, more brutal aspects have probably been toned down or eliminated since the uniting of the tribes. It wouldn’t be socially acceptible to drop a filly of the side of the cloud for being weak. Though old traditions die hard and many would probably think that if a pegasus is too weak to fly, then they should be taken to the ground one way or another.

v

@YoyoTripleThree
 
SNRK Bwhahaha!

@Feral_Socks
 
I guess Celestia didn’t do a good enough job of stomping out their Spartan-esque culture when she assimilated the three tribes into the glorious Equestrian Empire. I mean, why else would they put Rainbow Dash in charge of a civil works program? Yeah, she has all the qualities the Pegasus seem to treasure, but she is totally unfit for leadership.
 
First order of business upon The Master’s victory: All pegasus save Fluttershy and Derpy Hooves report to the Ministry of Love for reconditioning.

@Trickquestion
 
The second thing. It’s how they weed out the weak ones. Fluttershy just got lucky.

Why did that flight academy not have something like a… I don’t know, a lifeguard, safety rails, ANYTHING? I mean, they know a lot of the kids there aren’t good fliers seeing as it is a flight school for children. Were the budget cuts that bad, or are the Pegasus as a race (save Fluttershy, who has completely rejected her race’s traditions) just assholes?

I have a replacement Element right here!
 

 
Wait… Are we looking for a new Element of Kindness? This… This probably won’t work.

@Impious
 
Celestia: Well, damn. There goes my last element of harmony.
 
looks around
 
You! You’ll be the new element of kindness.
 
Roid Rage: YEAH!

@Pwny
 
It was common knowledge that she couldn’t fly.
 
“Fluttershy! Fluttershy! Fluttershy can hardly fly!”

DAW DAW DAWWWWW

And nopony bothered to look for her. Dash was busy celebrating, while for all we know (she was fine, but still) Fluttershy could have been impaled and rotting on a tree branch.

^ well she was shy so probably nopony knew her and just thought she could fly.

Then she was knocked to her death, and no one cared.

If she was a real race official, all the competitors would die of cuteness.

How they convinced Shy to be the flag holder I’ll never know.