The Harley f-slur episode did it for me. A couple years prior, my closest friends all got together and agreed to stop using the f-slur. We had no out queer friends (god it took me so long to admit dicks are good actually), and we were just "this is dumb to just use constantly". The word was so ingrained in our lexicon and a bunch of idiot 13 year olds decide amongst themselves that enough was enough. Then like 2 years later that episode came out. Was a quick "well this is dog shit" realization.

I doubt South Park often makes fun of smug enlightened centrism, apathy as a lazy response to actual political issues that actually affect living people's lives, or for that matter the rich white asshole libertarianism of Matt and Trey.

They embrace it. There was an ep where Stan starts drinking to accept things. It's literally "caring will make you unfunny, lonely, and lame".