This is becoming less about "are kids (in general) okay at breweries" and more about "there are a few kids (and their parents) who ruin things by being jerks". Sure, that's true, but how is that really any different from adults who ruin things (at the same places!) by being jerks. Some people are irresponsible idiots who do a good job of ruining a good time, and it doesn't seem to me that it matters much what tool they use to do it -- kid, dog, loud bachelor party, constant flatulence, vomiting on the floor, starting a fight, uncomfortably flirting with the server so the whole operation slows down, etc.
But then, I live in a college town where it's popular to visit local wineries. At this point, I'd rather see a 4-year-old in a brewery than a bunch of 22-year-olds.