I do not disagree with your assessment at all. And I *do* hate selfie-sticks.
But take away the selfie stick and any form of technology and I'll wager that the young man may have had a low-tech form of disregard for anyone else. The problem in your story, as I see it, is that the parents didn't say or do anything. I love kids (have a couple of my own), but I get really frustrated with parents who don't put any sort of boundaries on their kids' behavior. Had these parents addressed the child in the matter, I'll bet the selfie-stick wouldn't have been a problem past the first time. And had they attempted to teach their children how to be courteous before ever going to Disney, you wouldn't have had a story to tell.
Double triple like - and agree 1000%