The problem with "eject behaviors, not people" is that it puts a burden on the staff. People who are misbehaving often do not accept "you are behaving badly, please leave". They're often argumentative -- if they were polite, they wouldn't have engaged in that behavior in the first place. By the time they can tell that the behavior is a problem, it's more difficult to fix.

That's where these rules come from. The staff has to make a choice: tolerate the unpleasant behavior, or risk ratcheting it up to even worse behavior by intervening. It was bad for business, so they made rules. They knew it would cost something; they believed that the benefit was worth the cost.

I do believe that it's incumbent on adults without children to tolerate children to a considerable degree -- more than seems fair to them. But I've also found that a lot of parents consider "I'm raising the next generation and therefore justified in demanding infinite tolerance" to be valid, and that's just not right. When we can't negotiate a middle ground, extremes get set.