In my opinion (and in my novel), bikers are more accepting then most men, because they really believe in freedom. Most bikers I know (and I used to be a regular in a bar frequented by bikers in colors) strongly support my right to do what I choose to do with my life.
Moreover, the most sympathetically treated transgender character I have ever seen on television, was on Sons of Anarchy. One of the head bikers dated her, after the head-biker shot the transgender character's mom in the head, while the mom was verbally abusing the transgender character.