Yes, dying changes nothing about a person's actions, which is why not speaking ill of the dead has nothing to do with what they did when they were alive.

It's awfully easy to make someone out to have been "an asshole or a POS in life" when they aren't there to defend themselves. And it serves no purpose, other than to make you feel better, since the value in talking about horrible people from the past is in understanding their actions and what they did. Calling them names doesn't inform anyone about the history of that person, it just makes them emotionally charged against someone they never knew, and makes you pissed off all over again because you keep resurfacing the same emotional reaction to some dead guy from decades ago.

You can say "John Smith did this and that" without also adding "and that's why John Smith was a massive asshole!".

Now, maybe John Smith was a massive asshole, and we just can't help but point it out sometimes, but that doesn't magically make it the right way to behave, or the right thing to say in a given scenario.