Because of the characters he played. (ahem) "some of us" are able to separate a person's personal life and opinions, from the characters they play in movies.

He landed some great roles in lots of great movies and lots of mediocre ones as well. He was typecast as hell, "always played himself", but that meant that he was reliably a complex good guy he man, often with a troubled past. From movie to movie, his basic mannerisms and personality were the same, but some of his characters were deep, thanks to good writing. And he did not fuck up. He needed good writing, but he fit his characters perfectly.

See The man who shot Liberty Valance for a story worthy of Kurosawa. (James Stewart, Lee Marvin (as the worst movie asshole ever)).

He was popular with boomer boys, but then it became political, and he was easy to impersonate, so he became a joke. But we didn't know or care most of the time. And I mean, there are some roles he played, where I simply don't care what his politics were. He was good in some great movies. If you can't see that, maybe you're just a bit ethnocentric.

You don't have to like the artist to appreciate the artwork