I think it's different (and totally justified) when the majority of the memories are bad ones. However, with many people, that doesn't seem to be the case. For example, when my father died, years went by where my mom went back and forth, being angry at him one day, pining over him the next.
Eventually, I advised her that I was seeing this take a toll on her, and that while she shouldn't necessarily forget the bad memories, or even the feeling of abandonment, that the time for arguing was long past. Nothing further could be done to right wrongs on either side.

And that, I believe, is the real key. Once someone is gone, those battles will only be one sided. Any angry, loss, hatred, all piles up on the living, and cannot change the past.

I chose to actively remember the good things about my dad. When faced with a comment or memory that brings up the bad, I acknowledge it for what it is, and move on - because I do not want to dwell in those places any longer than necessary.

It may sound selfish - but this idea of only speaking well of the dead can often do more to protect the living, than to shelter the deceased.

Have no idea....my family went ape shit when our uncle died and I said he was an asshole...they got even more upset when I said they were hypocrites....

Commenting just to add photo via reply.

What do you do when a Mother or Father dies and you had a miserable childhood? When my dad died 3 years ago we had a fight one week before without closure. It was tough.

My dad was a ugly person in so many ways. I said nothing at his funeral. You heard the phrase, I've come to bury him- not to praise him.

I was raised with "if you can't say anything nice, don't say anything at all", and "don't speak ill of the dead". Both are things I have eschewed in my adulthood.
I won't go out of my way to be rude, but I'm also not going to lie.
If it doesn't matter how I feel about someone (except 45), I'll probably keep it to myself.
However, if someone I know, who has died, was a piece of shit, I'm not going to talk about them like they were anything else. Situational ethics apply. It all depends on the setting and those present. There's no point in deliberately hurting someone's feelings over all of it.

There is no point on beating a dead horse.

Where you at their funeral? I mean if not then totally justified. But if you're there at a funeral and they where a dick to you, why be there?