I've have seen many players play opposite genders in my game and not once have I seen a player use the gender to deliberately play the gender poorly, but neither have I seen them play the gender with any genuine depth.
Considering how rarely one ever sees any characterization with genuine depth, this should hardly be surprising.
I don't care what you play, just as long as you keep it PG. Anything that isn't PG, happens off screen and without elaboration.
I don't mind the occasional romance plot regardless of the player/PC mashup, but if I start to feel that in some fashion the player's sexual fantasies were becoming a large portion of his decision making as a player, I'd probably take them aside privately and tell them to tone it down. That would be true regardless of how the player chose to engage with those fantasies, what those fantasies were, or what gender that they choose to play. I'm not there as a DM to help you explore or express sexual experience, fantasies, or desires at the gaming table. That's a whole other spectrum of role-playing, that isn't part of what I do or what I think other players should be subjected to.
Beyond the obvious whose parts fits into whom differences that I'd rather not make a part of social play, I don't particularly find men and women all that different and certainly believe the range of experiences and abilities for genders is wide enough to encompass just about any PC concept. So I tend to not worry too much about whether a player is playing a gender right. Every characterization a player makes is going to be contrived and stereotyped. Heck, if it's badly acted, then it will probably be an above average characterization in that at least it will be acted out and consciously considered.
So far, abiding by those guidelines, I've never had anyone feel threatened. Nor have I ever observed big differences in what male or female players wanted to explore in terms of romantic or sexual game experiences (some play promiscuous PC, others chaste, some want no attachments, others prefer a romantic object of their affections), or in terms of exploring opposite gendered characters, or in terms of their interest and tolerance adult themes (pregnancy, marriage, family, etc.). Because of that, my bias would be to see anyone that wanted to break or stretch my guidelines, or anyone getting uncomfortable within PG framework, as probably not well suited to the table.