It's basically impossible I think to say if Jazz was going to grow up to be gay or not. One, that's usually impossible for kids you actually know, two, everything we know about Jazz as a young kid comes from either his stupid, dishonest parents, or fawning media coverage. Now, personally, I don't think Jazz's trooning was much driven by homophobia. Just his parents' (particularly his mother, but I think Greg gets let off too easy around these parts) grasping need for attention. Remember, they started down this path when Jazz was three. Three. A three year old child is about equivelant to an African Grey parrot at that point, and yet we're meant to believe Jazz was giving monologues about their sophisticated gender identity.
This is why people treating "social transition" for kids as baby steps are either stupid or lying. From the age of five, Jazz was introduced to everyone he knew as a girl. He was told by every authority figure in his life that he was a girl. Anyone who disagreed was posed as an enemy. He was told continually that his male body was broken and wrong, and that his real life could begin once has was surgically modified. His puberty was treated like a degenerative medical condition. If all of that wasn't conversion therapy, I don't know what is.