Many are guilty of this, but still—bartenders (and other bar employees) shouldn't have to deal with your impulses. Don’t fuck around (or fuck) in the bathroom. It’s not romantic, it's not sanitary. Being this nasty is, in fact, a huge health code violation for the bar. The amount of bodily fluids (and solids) that end up on those floors and walls by night's end would blow your mind.
Do everyone a favor and just take it home.