It's fun to kvetch about such stuff, but you have to keep it in perspective. I kinda ruined a viewing of the re-release of Spartacus a few years back by pointing out my friend that one of the battle scenes had cavalry using stirrup'd saddles - stirrups were developed closer to the middle ages, I believe.

I thought I was so cute & clever to actually know stuff like that, but the detail bothered my friend enough to wreck the experience. Nowadays, I make sure I save any stuff like that for the 'after' discussions.