My brother almost put his Lab/Sheperd cross through the frick'n wall when he tried to do that to his 8yr old daughter. I had a buddy whose dog humped everything. It was annoying as hell and embarrassing for the person getting humped. It got to the point where we stopped going over. Ass hole used to bring the mutt to softball tournaments and laughed when it humped someone's leg, ball bag, garbage bag... whatever. Then he would try to fight when someone got pissed and lashed out at the dog.
It's useless pet owners who let this shit happen that need a good smack. It's not funny and you have to get a grip on that shit from the first time it happens.