I’m 63, and though I have seen it used in memes I never thought of it as a pejorative. Maybe in a mild joking sort of way? Are people really insulted by this?

Well, people have stopped using it literally, so I don't see what it can be except a pejorative for subjectively "old" people, usually. If you actually argue that people younger than about 55 aren't boomers, you'll just be told that's not what the word means any more.

If you are a boomer, then I agree, why should you feel insulted?

Almost every case I've seen has used the word in a dismissive, ageist fashion. I think it's similar to mild ethnic slurs like "yank", "limey", "frog", where the target has similar or higher status.

At best it is lazy writing, and most commenters on HN write better than this.

See https://en.wikipedia.org/wiki/OK_boomer

I think baby boomers are not as fragile (as some other "groups") and don't get offended by someone calling them a name.

There is no one kind of person in a generation. But, I have noticed that baby boomers tend to tout the philosophies of grit and self reliance of their elders while being as self indulgent as possible.

Therefore they expect others to suffer quietly or be seen as weak, while any restriction of their own desires is tyranny.

https://www.fatherly.com/love-money/baby-boomer-parents/