They had a massive platform at a time of major social upheaval and they didn't really say anything about race.
The problem with that line of thinking = it would seem the only solution is that every single artist of every single medium needs to be talking about race/politics or face a backlash. Some artists don't like to get particularly involved, and they don't automatically deserve criticism for it - especially not from some highly-educated overly-PC person who happens to not also be a real scholar of the band. It's like there is some magical amount of "expected" political engagement that some random educated people have randomly deemed necessary for an artist to have had - a completely arbitrary amount that is literally pulled out of their butts - and somehow this measure of expected engagement is fodder for criticism and clickbait articles, if the artist they deem as deficient does not measure up.
I get that it would be cool if the band had done a few more socially conscious actions in the '60s, but I don't think it's fair to fault them for it. I don't fault ABBA or any of the disco bands for having song topics that are mostly apolitical either. It's nobody's decision but the artist, and really unfair to label the artist in a negative way simply by some random person's perceived reasons for the artist's inaction.
And yeah, as you also mentioned, sadly the more politically-minded songs from SMiLE wound up being unreleased. And the lack of the general public being aware that those songs - with progressive political lyrics - means that the band is once again being unfairly judged. The judgment is misdirected; any judgment should be directed towards any actions the band does *actively* promoting someone with abhorrent views.