Yes because the lavatories we are talking about are public/shared access which means people are free to make the choice. Now don't get me wrong if I was about to walk into one and someone expressed their urgency to lay a cable, I would let them take the cubicle. But if I was already in it, chances are I will be done in 30 secs and if the timing is so bad that someone who just happens to have colitis, Crohn's or something similar, turns up then there is really nothing I can do about it.
If the robgmun has such ****** (excuse the pun) luck that every time he makes a run for the loo he comes across a cubicle pee-er then he needs to go see a white witch 'cos someone has cursed him really badly.
I know I sound really insensitive here but it is more in annoyed reaction to his insults and assumption that his health condition gives him unconditional access to a thunderbox...