“Meathead”, Archie Bunker’s son in law, was the caricature of a liberal who was so open minded, his brains fell out.

For that time period, probably. Not sure that would be perceived the same today. Been so long since I watched it, I couldn't say for sure.

Within that tension, “All In The Family” portrayed the conflicts that played out in America at that time.

Sometimes successfully, sometimes not, but the series did provoke its share of discussion- back in a time when discussion still occured.

Agreed. And while some people saw themselves in Archie (as another poster mentioned), I think some realized the silliness of what they saw, and maybe rethought their ideas. Archie was basically holding a mirror up to the bigoted American.

...no new thought could penetrate his skull.

And it wasn't always social/political. I have no idea why I remember this exchange, but I do... Meathead was putting on his shoes. He put on his sock, and started to put on the shoe. Archie said something like "what are you doing? You put on a sock and a sock, and a shoe and a shoe". Meathead responded "I like to finish one foot at a time". It was silly, non-political, but part of Archie's inflexible, unadaptable character.