If there's an option for our male vampire to seduce a human male, that's because our male vampire character thinks that's a viable option for this particular individual. Anything else is trial and error(bad design) or Bioware style wish fulfillment fantasy(fake and gay).
A better way would be to leave those kinds of deductions to the player, after all there must be many disciplines in the lore that would help a vampire get inside someone's head, in Bloodlines there's even the malkavian whispers and possibly high auspex thanks to Wesp. The whispers don't actually offer anything concrete enough for you to alter your path radically, and even if they did you still couldn't do so anyway, but a complex game could make even that possible.
Limiting the occurrence of those seduction opportunities based on what your character is supposed to think, is just an excuse for limiting player agency and game complexity. Real life is often about trial and error and subtle messages, and the more believably games are able to mimic its mechanics, the better.