It's also worth remembering that we are legislating for the long term, and it should reflect principles. Laws based too closely on particular instances are often quite poorly crafted, either leaving things out, or not anticipating later effects.
Totally apart from more rare instances, the social setting can change, sometimes significantly. I don't actually have a hard time at all imagining someone straight being beaten up or harassed for that, in certain settings. I don't think I'd have thought it likely 20 years ago but the social contexr has changed a lot.
Over 20 or 30 or 50 years you can see big changes, and what's more, sometimes in very surprising ways. Why wouldn't you look at the supposed principle - crimes predicted on sex categories are especially heinous?
I think probably the reason some want that is because actually, what they really want is to, not discourage targeting certain types of divisions, but actually they are looking to set up new hierarchies. The's the nature of identity politics, not an abolition of conceptual hierarchies but creating a new set of them.