There's a trick I learned about public loos when you just have to use one;
pretend to get your plonker out for a straining, then when the usual bent scumbag shuffles over to choose the empty urinal next to you (when all or most of the others are empty), you simply either walk away, or mace/pepper-spray the bastard and discourage the slime from ever slithering over your way or soliciting for lewd acts among the sewage.
Nice!
(this post is not aimed in any way at generalising about gays, some of them are loving and romantic toward each other and not interested in bothering normal [as in going about normal business] young men in public places. Those sensible gays are a credit to their sexuality, the weirdos simply aren't)