Nobody really believes Democrats can't be 'evil'. Not sure what gave you that impression. Fuck, most people admit we're voting for the 'lesser of two evils'. I don't think anyone is pretending Joe Biden is some saint who'll lead us to the promised land. (You're thinking of Trumpers who worship at the feet of their orange messiah). He's just really fucking better than the alternative. I'll take the Democrats brand of Evil over the Republican's brand every day.
"Tradition" is just a word people use to make themselves feel better about being an asshole.
