
edit : 20 ponies ... that must be roughly 20 rage-quits ... for that you get a 
Ponies are generally an easy kill

If they think their plane is superior to yours (overall) they'll typically try to turn with you for the quick kill.
The problem is...a pony doesnt turn so well compared with almost anything

Unless the pony is using BnZ and to a lesser extent energy fighting, they are a very limited threat, something you can usually determine as soon as you merge.
It seems that the typical mustang driver figures he has the best plane and therefore can do whatever he wants because well...its a P-51! Regardless of tactics and any knowledge about what his opponent is flying.
After the merge if a pony breaks hard, he either really knows what he's doing (unlikely most of the time) or he's thinking he'll get a quick kill, or unfortunatley....thinks he's going to get the best out of a turnfight.