People are never more dangerous than when they convince themselves they've found a "perfect" moral justification for their actions. "Divine Right" justified centuries of tyranny and misery. Racism justified slavery, Nazism, genocide. Religious bigotry justified missionary colonization, residential schools, cultural genocide, femicide.
And for the Democrats, the perfect moral justification has become "but Republicans are worse!". This props up an aggressively, even proudly, amoral realpolitik where the ends justify any means. Beating the GOP and "saving democracy" means it doesn't matter how many lies they told, how many women Joe groped and sniffed, how much money his wastrel son was paid for plum jobs, how many wars they started, how many covid deaths Biden's soft denialism caused. Victory at any cost.