Do you think that it's fair to make a generalization about a certain group...

It is actually just laziness. People can't be bothered to separate one person out of thousands that may all act the same so they just paint the entire group with the same brush cause it is mentally easier to throw away one good one instead of going through the struggle of dealing with 999 bad ones for the sake of a few good ones.

Doesn’t need to be bad experience, just use fate of birth. Those that accept astrology make group stereotypes based on a calendar.

Generalizations are never fair

I know!!!

No, it’s very unfair. And usually the person speaking certainly wouldn’t want it done to themselves.

That behaviour had been normalized quite some time ago