Yes, only in a subtext or profile field instead.
Well you say, we might have a problem with people discriminating against non-norm sexualities and roles (homo, bi, tranvest, transgend, asexual [they exist but not in the reproduction sense]) being discriminated against.
Easy. Report the dildos responsible for any discrimination.
This idea would actually probably straighten things out and avoid awkward situations as well, and encourage people to talk when they would hold back otherwise.
I don't see why this should be such a big deal. Now for those who find this indecent and prefer to only view things approved by Jesus Christ/Allah/Yahweh/whoever himself you could just make a "hide sexual preferences of other users" option.
Now this just means another description field. Not outright sexual advertising. Save that for your bio.
That's the way I'd prefer it done anyway. Not so much a screen as another field or sub-text under the screenname.
But if you want to indicate your sexuality in your screenname I have no problem, but it's more prone to cause outrage and those who would prefer to not see it can't do anything short of blocking your user.