If you knew someone was a serial rapist & murderer, but they volunteered at homeless shelters, donated to charity and fostered rescue animals, would that “balance it out” enough that they aren’t evil anymore?

The problem here is that this view is binary. There is no middle ground here. In the real world you could be pro some left-wing ideas and pro some right-wing ideas. This is the problem with bipartisan “democracies”. As a centrist you are always the enemy.