Polite? Rude? Just try the handle and be damned?

http://www.slate.com/articles/life/culturebox/2013/08/knock_on_the_bathroom_door_you_owe_it_to_the_person_who_might_be_in_there.html

I was once using the facilities on a train, had only been in there 30 seconds when some chirpy entitled kid banged on the door and said 'excuse me, can you hurry up please?' Fuck you buddy, let this be a life lesson that the toilet is not always there when you need it.