Can I support transgender rights but hate the only trans person I know?
Why do you hate this trans person? Tell me more about it.
He is so aggressive on some issues and so ignorant about others
You are great for trying to be an ally and understanding marginalized people like trans. But your friend shouldn't be hated, he needs to be understood. He has different viewpoints than you because he is trans, so you have to listen and not judge harshly.
I'm terrified of this person and that I might get in trouble for hating them.
People are scared of what they don't understand. I understand you are terrified, but once you truly get to know him, then you will probably not be as scared. What you are doing is right, and it's good to support transgender people, so that should also include your friend.