I think it is amusing because it is a different way to look at senior citizens. The stereotypical view of a guy that age is a benevolent old man who just smiles at little kids and floats along happily without much going on upstairs. It is funny to think that inside he is a regular guy with the same goofy, sometimes nasty thoughts as youngsters. I didn’t find it at all offensive, just mildly amusing. I had a whole backstory going that Grandpa is a surfer from way back and takes offense to posers, just like young people do nowadays, even if the poser is 3!
I honestly cannot see how anyone is considering that child abuse or a joke about child abuse. The joke is that what the grandpa is saying is inner dialogue he isn’t berating the kid. Seriously people, none of you have ever witnessed something done, said, or worn by a little kid that caused a negative inner dialogue?
If the young kid sees it? Well honestly that kid is way too young to be on social media so that is on his parents. When he is old enough to be on social media and does see that meme, he will more than likely actually get the joke, especially if it was one of his family members who created it, because he will be familiar with their sense of humor.
There is really a lot of righteous indignation here that could better be directed elsewhere.