Well the anon above me is just lovely, isn't he? Interesting story. You definitely shouldn't feel disgusted by this, though I don't think this is the best place to seek advice or comfort. It's hit or miss with who you'll encounter, and there's a lot of assholes on this website. Not pointing any fingers *cough* guy above me *cough*.
Well, then he's just controlling. Dump him and move on.
That's not it at all. It comes down to interest. He thinks that if you are with a girl, you'll put your interest more into her, which you are very obviously doing. If you're with a guy, he probably thinks there's less chance of you finding him more interesting, since he's monitoring it. Also, some guys are just controlling. That's a thing that happens, don't rule it out.
Being in a relationship does mean you have to compromise, though. So if he doesn't want you talking to her, you should probably respect his wishes. Just like you hope he respects yours in not being with another guy in front of him.
That's actually all entirely untrue.