Some people probably don't see any issue with the generalizations for a few reasons. The first is that they have had generalizations applied to them and successfully avoided negative consequences. The second would be people don't see any harm in them at all because they feel the shoe fits everyone, which I agree isn't a good way to think of things. And I think the final reason is that generalizations can be helpful in managing a difficult conceptual problem.

Certainly if we simply stick to the idea that all of group A is terrible then the conversation stops and nothing productive is gained. However, if we get caught up on nuance and language too much, the conversation also stagnates and it becomes difficult to come up with measure able solutions or to discuss potential widespread beliefs or cultural implications.

We could be more careful and mention that it appears some in the group seem to adhere to a "I want everything" mindset, and perhaps that precision would allow for a better discussion philosophically or even practically, I really don't know, but I think some generalizations are useful in a complicated problem like this.