I hate it when people do that. The Afghans are notorious for this but we have to let them in our gym. But they will bench press 55lbs (Yes I mean 55lbs including the bar) with horrible form and just sit there on it for like 2 hours.That and they will also use the squat rack for curls and half presses. It infuriates me to no end.
I actually organized a one day class on weightlifting for them and took over 3 hours to go over everything. They of course didn't pay attention and do the same weight for the past months with the same garbage form.