Phobia: an extreme or irrational fear of or AVERSION to something. Note AVERSION. Being against trans people and denying their existence as who they are, is, in fact, transphobic.
People use this whole "transracial" thing as a way of mocking transgender people. "Oh, you think you're another gender? Well how about I say I'm a different race! Gottem!" And also, a phobia is a fear of aversion to something. So, if someone is against gay people, they are homophobic.
