As far as I can tell, Rittenhouse ONLY took a photo with those guys AFTER the shootings, and only because they came up to him asking for a photo. The kid was 17 at the time and I suspect he was more of a useful idiot than anything. I mean, I wouldn't have known who the Proud Boys were when I was 17. If I'm wrong, there should be evidence (FB posts, Twitter feed, etc.) that Rittenhouse had white supremacist leanings.
But let's say you're right and he did - does that mean he's not entitled to equal protection under the law? I'm a traditional liberal of the John Stuart Mill variety. Each individual is entitled to the same rights regardless of whether or not he or she is a bad person. When we start dehumanizing people based on their beliefs, we get the Holocaust.