> How saintly of you to never have such a lurid thought.
Some people--a lot of people--just don't have those thoughts. That doesn't make them better or worse than people who do; both can do good, or harmful things. I think the point of GP's comment was that there are many of people out there who simply don't feel that way.
There are a lot of ways that might play out: they might not be attracted to others until someone is attracted to them; they might be attracted, but have no automatic desire to turn that into action/hitting on people; they might not be attracted to others period, et cetera.
> The urge to hit on a woman you find attractive ... makes [you] a straight/bi male
You're still assuming the two go hand in hand. Your impressions might be confirmation/selection bias: people who don't have the urge to hit on people they find attractive are going to be less obvious to you (insofar as they are competition for people you find attractive), and are also likely less inclined to jump into public discussions on the subject, given that a lack of sexual aggression is, in many demographics/situations, a basis for shaming.
Edit: punctuation.
