Would telling him this make me unsupportive?

Ny little brother recently came out to me as gay. I kind of already knew over the years, I just let him come to me. He's 16.5, I'm 22. I was the first person he came out to. He wants to come out to our parents, but I really don't want him to. Our parents will actually hurt him. My dad used to abuse his bisexual brother just for being bi. He used to beat on him and call him a faggot and its why we don't see my uncle that often because my dad hates him. My mom will also let my dad do it because she hates gays. I understand he wants to be out but I think him being safe is more important. I think once he's moved out he can come out to them from a distanced so he's safe. I hate to feel like I'm pushing him into the closet though. Am I a terrible unsupportive sister?