Instead, how about you just not assume you can tell what is going on in someone's house based off of your obviously limited experience with children and one post on an internet message board.
I really don't appreciate your reply. It comes off as assuming that I'm basically an idiot. "Oh, just tell the children no!" Yeah, that doesn't really work when you have highly intelligent children you've been raising to be rational, thinking agents. They may not be developed enough to value long-term health issues over short-term pleasure gains yet, but they certainly are skeptical enough to call out fiat answers as bullshit. I'm actually rather proud my children argue with me so much, despite how exhausting it can be.
Hence me targeting my ire at the damn ice cream truck. It's not my children's fault they want ice cream (they are children) or that they are elementary school lawyers (I have certainly encouraged it, much to my in-laws' ire). It is the ice cream truck operator's fault for employing marketing tactics aimed directly at children. I keep my children off of cable TV and pay for streaming subscriptions to keep them away from completely unadulterated junk until they have brains developed enough to see through it, but this guy injects it out of my control.