Of course they're not - that's a pointless thing to say. Hetero "activities" as you describe them are clearly impossible in a locker room environment because the sexes are separated. But put a lot of naked men together in one room with sweat and hightened pulses, and they're going to start looking at each other. And there's not a damn thing you or anybody else can do about it. It's the nature of the beast.
This is one of the dumbest things I have seen posted. You mean you can't hold back for 20 minutes from wanting to have sex with someone? The nature of the beast. This is ammo for people who want to keep gays out of the military. If anyone from the Army were to read this, the don't ask don't tell repealers would have some explaining to do.
If you are that horny, get a room.
As for the towel. standard bathroom etiquette is eyes forward. So now you are going to have your junk on display and as someone pointed out, possibly brushing up against parts of the bathroom sinks that others will touch. We have people who won't touch bathroom door handles. They take a paper towel to open it, but you could put your cock in the sink. Nope.
I played sports year-round in HS and seasonally in college. We never walked around naked. Common courtesy was to wrap a towel around your waist. It doesn't hurt you in the least.
Lastly, it should not be accepted that having sex in a lockeroom is ok. If my gf and I were alone in there I would admit I would be tempted, but if we were caught and they threw me out I would have no complaints.