Despite the horrible things people do and believe on this Earth, it's important to accept that they are as human as you, and they have a life that they lived full of happiness and sadness, love and hate, various other emotions. It's easy to feel the disconnect between you and the second-in-command of America's most notable hate group, but just acknowledge that there are family members that are mourning his loss. He's not some 'tribal white scum' but rather a human, and although he follows the same group that terrorized my grandparents and great grandparents when they were alive, he's still a human being.
Put the hate aside and try to see this, give a moment of silence for his family who are probably grieving right now.
you seem to be under the impression that everyone here doesn't already know this
there are some people that, when dead, present a net gain for society. allow the people who are close to him to grieve, but know that some people are better off having no influence over anybody. while sudden death is not ideal, it solves a problem. a problem that would ideally be solved through convincing and conversation, although near impossible at this level of indoctrination.
it's the same reason why nobody cries about Riddler's death. ideally, he would be put through therapy and shown the wrongs of his ways, but that is incredibly unlikely and there were no significant downsides to Riddler dying. sure, Riddler's family probably felt bad, but that's between them and their personal relationships. it's rude to force those people to whom he was personally connected to feel happy about it, but it is entirely unreasonable to expect society as a whole to remember that Riddler was a human being when they are busy celebrating their freedom from his dictatorship.
this is a really long-winded answer with respects to your moral beliefs, but this is the nicest way possible of saying that this person held such little value in society that it's probably a good thing that they aren't around.
