This is a ridiculous thing to say. No one would go to a kid for a colonoscopy, and if they were stupid enough then they deserve what they get. Common sense says that adults should be licensed for dangerous operations because the customer can't tell by looking if an adult is trained to do the operation or not. You can tell a kid is not a doctor simply by looking.
Back to lemonade stands: use your common sense. If kids are running it and you don't trust kids' hygiene or ability to make lemonade or whatever, don't buy the lemonade. There is no possible reason why a license is required.
Right, you are repeating what I had already admitted, that my example is ridiculous. My response was to the suggestion that we should get rid of licenses and just let people run their businesses. In some cases, this is fine (and in these cases you probably don't need a license, programming is an example of this.) In other cases, not so much.
I'm thankful for the U.S. being strict on food safety / handling standards. I'm currently living in the Philippines and I had traveler's diarrhea for the first few months I lived here and I still get it regularly after a few years. Common sense helps, but it only goes so far.
Back to lemonade stands: use your common sense. If kids are running it and you don't trust kids' hygiene or ability to make lemonade or whatever, don't buy the lemonade. There is no possible reason why a license is required.