Rude People

I've just been trying to mind my own business of late and now, I can't even focus enough to work on my story line for the rp i'm supposed to GM because I'm so upset.

I flipped out one someone, who used to be my friend, because they were rude and talked sh!t about everyone they knew and now they've turned all of my friends against me. I can't even go to anime club any more because everyone there now hates me. I've been trying to ignore it, but it has me in such a knot. I wish I could just get on with it and just do the things I enjoy without this impairing my ability to do so.

A good question to ask yourself in this situation is first (or, the one I ask myself anyhow)
Is there actually a problem? Paranoia can make a lot of things seem a whole tonne worse than they really are, and things like stress and other factors worsen it. After that, really, it's best to ask if they have a point. Depressing as it seems, learning to grow from the criticism of others, even if not constructive and just malevolent, is a great thing to have.
Then there's talking with people. It isn't something I do, mainly it's just passive-aggression and dour looks, but that's since I'm past caring. Talking it out can make a lot of problems into something that brings people closer. Maybe this guy isn't that bad a person. I dunno, I can't say anything about it, since I'm not you, but I get what you're feeling :<