I make a distinction between manners and etiquette - manners as the principles, which are eternal and universal, etiquette as the particular rules which are arbitrary and different in different times, different situations, different cultures.
I lived in a world where social arrangements were taken for granted and assumed to be timeless. A child's obligation was to learn these usages, not to question them. The complexities of racial deportment were of a piece with learning manners and etiquette more generally.
Let's face it: professing a deep interest in movies, the absolutely dominant global art form of the last century, is at this point like professing an interest in air. Passion is nice. Erudition is admirable. But it's like that moment when good manners cross over into meaningless etiquette.
Etiquette does not render you defenseless. If it did, even I wouldn't subscribe to it. But rudeness in retaliation for rudeness just doubles the amount of rudeness in the world.
When you've been brought up in variety, I think timing is always important in your life. If I'm ever late for anything, whether it's personal or business, I always apologise. 'I'm sorry I'm late,' and all that. And if somebody is late meeting me, I expect them to say 'I'm sorry I'm late.' It's just, shall we say, showbiz etiquette of my day.