I've grown far less tolerant. Maybe just in movie theaters. I will not hesitate to notify ushers, security, management, whoever is supposed to get notified about disruptions, if someone's kid is being a disruption for more than a short period. Or repeatedly over numerous short periods.
Is their kid disabled? Perfectly abled but still a little monster? On medication that makes them irritable? I do not give a fuck, get out.
Oh, also libraries. If you can't stop your kid from screaming non-stop, get the fuck out.
I put up with noisy ass kids in restaurants, malls, grocery stores, on the train, in the park, all over the place. I game with friends who have four kids ranging between 8 and 1, and aside from the occasional physically painful shriek, I don't bat an eyelash at them being little monsters, but if they brought them to a movie theater and those kids couldn't control themselves? I'd have their asses out in a heartbeat.
Which they know, and so they don't take their kids if it'll be a problem. If that means they just don't go to movies if they can't make arrangements, then it does. And yeah, it sucks for them, but too bad. They chose to be parents, not the rest of us,. There's other places, other ways, you can go out and get your public on where people will feel obligated to put up with poorly behaved (for whatever reason) children. The movie theater isn't one of those places.