The real issue here is it’s hard to revise such emotionally charged views in light of new information. Condemn people for murder and it will be harder for you to notice the innocent person on death row.
Worse, many people will try and influence your opinion via misinformation. Condemnation short circuits peoples ability for rational though and that’s exactly how normal people end up committing atrocities.
But of course: isn't that the important lesson? Most, but not all were; so is this knowledge an excuse to do nothing or is it a spur to look for the injustices one accepts today, and change one's position?
Beware anybody or anyone who seeks to erase the messiness and complexity of life. The pursuit of purity is the root of so much evilness. If you uncover the sordid past of a public figure, the right thing to do is exhibit that history alongside the better things they're known for, so that people learn and remember what real people look like; that nobody is a caricature; and that to avoid repeating the sins of history we must appreciate what we share with those who have committed those sins previously.
Yes, I even consider the Nazis terrible people no matter how widespread antisemitism was at the time and no matter how much public support they had. I have that view simultaneously with the understanding that there is no German my age who engaged in any of that.
There is nothing wrong with understanding and making moral judgements about people. I can look at a painting in a museum that has someone enslaved in the picture and both understand the context and be repulsed by the depiction.
It's proper for people to make moral judgements, and to understand both past injustices and contemporary injustices that one implicitly (one hopes not explicitly!) supports.