I keep on hearing “but he is evil / they are evil” therefore we can dispense with niceties and treat them the way we feel morally justified to. This usually starts with baiting arguments on Facebook towards people with unpopular opinions, but people have been open about increasing their invective towards whole categories of people.
NO. It does NOT work that way.
Moreover people who so simply ascribe “evil” to people who rape/spraypaint swastikas/“are racists”/kill kittens suffer from a just as infectious form of evil: the banal kind. The kind that refuses to acknowledge reasons, seasons, ignorance, and redemption. The kind that goes along to get along.
And another of the very excellent reasons why we don’t dispense with a baseline to justice that presumes some level of humanity in the other is what that does to you, as the vigilante, or as the person who supports vigilantism. Slippery slopes aren’t considered valid by formal argument methods, but a fundamental of at least one framework in ethics is the one of universal application. If you can’t have everyone doing it to the same degree, then exceptions should not be granted the moral rule.
Finally one more thing: the purpose of “evil,” perhaps most especially the banal kinds, as they take the most work, is to call forth the concomitant response of the good, and change the way we think about things. Operative word: think. Feelings are perfectly valid information, but thinking informs them.