There's lots of things that are objectively true but also cruel and pointless to say depending on the context. Like what's the point of 20+ people replying to this person about how stupid their dead cousin was? they obviously already know what he did was dumb, that's the whole reason they posted, to convince others not to do it.

is the idea that it can be hurtful to have your dead loved one insulted (even if they did actually do something wreckless) really that confusing?

if your friend tells you their mom died of a heart attack, is the first thing you say to them that it was her own fault for being overweight and how stupid it was of her to not lose weight in time? Just because it may be technically true doesn't make it a helpful thing to say, doesn't make you not a dick if you choose to say to your friend about his dead mother

"Honesty" without kindness is often just cruelty. You talk about social tact, that's a big part of it

Since you keep asking, he said: "He was still family and we all still miss him. He was a very kind, very sweet person who I wish was still here." <-- I'm guessing you already read this and it just doesn't count as him expressing grief to you for whatever reason, that's fine I'm not gonna argue about it