i'm kind of an expert in dealing with bullies.
you need to throw it back in their face. you can't just match them, either, you have to escalate at every opportunity. and, you can't give them a chance, because they'll abuse it. you can't show any empathy - they'll just take it as weakness.
you'll find the odd masochist jock that isn't smart enough to develop a sense of self-worth and enjoys being berated because s/he sees the exchange as some kind of competition to win. these are the worst, but you have to win the competition. you might not particularly care for their respect, but getting it is the only way that they'll leave you alone.
for the rest of them, you have to aim to embarrass them and intimidate them into shutting the fuck up. you want to say the meanest, harshest things you can imagine. you want to go for the jugular and the crotch at the same time. and, you want them to walk out of the exchange so dazed and confused and shattered and broken that they'll never even look you in the eye again.
i don't like this. but i'm a realist. and it's reality.