Those examples aren't the same, as they are perceivable characteristics -- and obviously what you can see and hear plays a large part in sexual attraction. You have no way of knowing about genetics unless it's disclosed to you. It is letters on a piece of paper.
I concede those examples aren't entirely comparable but what of a criminal? If a murderer is out on parole nobody will know unless he reveals it. Having committed an act like that in the past is enough to creep some people out to the extent that they might not want to have a one night stand with you. Question: Should the feelings of a potential sex partner be respected in that case?

There are people who, without question, are going to feel wierded out if they actually knew they were sleeping with a transsexual. Should those feelings be respected, even if its a one night stand?