Don't be a drag, just be a queen.
But seriously, it depends on whether or not the transsexual was pre-op (meaning it has/had a dick at the time) or post-op (meaning it has/had a vagina). If he had sex with a post-op transsexual, then it is really no different than sleeping with a woman - just with a deeper voice and a vagina that used to be a dick. Now, if it was a pre-op, then he is most definitely bisexual/gay.