Sexuality isn't a binary black or white, straight or gay. Even the 2-dimensional sliding scale between homo- and hetero-sexuality they use in the social "sciences" is quite inaccurate. It's about what truly arouses you and makes you go "wow" inside (or out). Any attempt at justification or categorization is due to external influences, such as the ultra-judgemental views of society.
If you consider a man finding a ladyboy attractive as being gay, then you'd have to consider someone being attracted to a full female-to-male post-op individual as straight. If you have to check chromosomes before deciding whether you are attracted to an individual or not, then that's not being straight or gay, that's just being stupid.
