There are so many different varieties of sense of humor. It varies from culture to culture, generation to generation, family to family, and person to person.
It's one thing if a joke is actually harmful, of course. But, beyond that, I'd say that denigrating someone else's way of being whimsical is a specific subspecies of taking yourself too seriously.
The person you are responding to did not denigrated anything.
He responded to claim that if someone does not like those messages, then he "take himself too seriously". The response simple explained that author find those jokes unfunny.
As you said, humor varies from culture to culture, generation to generation, family to family, and person to person. That implies that not liking some kind of humor is completely valid sentiment.
There's a difference, though, between simply not liking some kind of humor, and publicly making fun of it.
I generally think that this advice is over-simplistic, but this tends to be a situation where the, "If you can't say anything nice, just don't say anything," principle really is a good rule of thumb.
If you insult someone for not liking the humor, it fair play from them to make fun of you back. And that comment was not making fun, it was expressing how that humor comes off.
Because what you want here is one sided "one side get to insult the other, but other is expected to not even express their opinion."
It's one thing if a joke is actually harmful, of course. But, beyond that, I'd say that denigrating someone else's way of being whimsical is a specific subspecies of taking yourself too seriously.