I think the reaction is at least partially based on the loss of precisely that certainty: there is a sense of comfort in that no matter how unacceptable someone

I think the reaction is at least partially based on the loss of precisely that certainty: there is a sense of comfort in that no matter how unacceptable someone’s actions or ideas are to us, they will die, regardless of who they are — eventually. The thought of that eventuality becoming unusually distant in the future threatens that comfort. Doubly so when only the powerful will live longer, which will come first, everyone seems to agree.