Wow , the amount of times this has happened with my friend..
Clearly, when they're together they
know they can walk all over you, so as its been said prove them wrong. What really pisses me off is when im angry and shouting - and the other person just laughs.
However, they're obviously not as tough and big as they think as when their apart they're fine.
There not real friends, tell them where to go. I sense that you don't want to do that go, maybe im wrong i just get the feeling from your post.
Honestly,
I would tell them tofuck off, and give them a nice long speech about how they're immature etc etc!