On the other hand I rate every single driver 5/5 almost without fail, even if they were rude. I figure if their livelihood relies on it then I'd be an asshole if I didn't metagame the system.
You aren't metagaming the system, you are being gamed by the system. Uber isn't as concerned that all the drivers are polite, but they do want them all to have near 5-star ratings, so if anything goes badly they can say “Hey, he had great reviews from riders up to that point”. If they guilt you into rating 5-stars for rude service, mission accomplished.
I do the same, unless I feel my life is in danger (reckless driving). Why punish someone who might be working for less than minimum wage?