Hmm...I gotta say I'm actually for it as a straight male, but as a straight male I don't like the idea of having the option for my character if that makes sense, because I don't feel he swings that way. Honestly what I think they should have done is make romances an optional setting. For instance, if you turned off romance of any kind, anytime there was a flirt option it would just be a different standard option instead. But you could do that with either same sex or opposite sex. That way someone playing a straight character wouldn't see that his character potentially wants to hit on those of the same sex, or vice versa even. Or you could leave on both or turn both off. It's too late for that now as it would require new voiceovers for tons of options and the like, but on the implementation of same sex I feel it's something that could be done since it hasn't been implemented yet.
That's toggle-talk, which has been ruled discriminatory by the mods (though I get that's probably not what you're intending to convey). Remember the dialogue options (all of them, not just the flirt options) are optional, so you can simply avoid selecting anything that might initiate a romance with the same gender as the character you're playing.
Put another way, as a straight male you probably don't have a habit of going up to men and flirting with them. You could, nothing physically prevents you from doing so, but you don't. Same deal in-game. You could (well, in theory, once the options are implemented) but you choose not to.