I'd add (probably also dodgy):Reasons to stay in a film you aren't enjoying/hate:
Your companions are staying in
You are being paid to review it/Some academic reason
You are tied to your chair with a gun to the head
You want to loudly proclaim how shit it is to annoy the other cinema goers
And, frankly, one of those is a bit dodgy.
Other people are walking out for bigoted reasons and you don't want to give grist to their mill.
(I wanted to leave My Own Private Idaho cos I thought it was pretentious nonsense and I was really bored but loads of people were leaving with much tutting about gay sex and rent boys so I stayed. )