People can be pretty mean, can't they?
I think that it might be (if you just came out to them) the shock of hearing this pretty major thing from you, it might just be a stage of denial. He could be trying to see if it's some test, or just in disbelief, I think.
If you want advice on what you could do, I have some words for that.
In the end, I wouldn't lose hope on him yet? There might be a chance of saving it, but if he doesn't support you, it's important to not feel like it's the end of the world. There's lots of people out there that will try to repress people like us, and although it would be nice if he wasn't, there's always a chance anyone could be. If I were you, I'd let it sit, let them process for a little while, then maybe bring it back up to them in a time when the mood is high and people seem calm, you know?
Either way, I know how it feels to be rejected by your (not yours specifically

) parents and I wish you hadn't had to go through even a little bit of it. Nobody deserves that. But it's inevitable in the end, and we just have to deal with it.
I wish you best of luck on making it all work out for the best, and I hope you have a great night/day, wherever you are.