So charcoal is pretty obviously stupid. But can we dial in a bit on the problem with a propane burner? Lot's of homes use propane stoves inside, which are plumbed to a large tank outside. So let's not say indoor propane burners are stupid and just leave it there. Don't get me wrong here, I'm not saying it's OK, I'm just saying that the thread jumped from a serious request for assessment to a comparison with charcoal to a disparagement of Bud drinkers. OP raises a serious issue, so let's not throw away credibility in answering.
I've always thought the risk was focused on the potential for leaks from those soft lines. Outside, any leaks can't concentrate; inside leaked gas could be an explosion hazard, esp with the tank right there. These burners burn more gas than a conventional stove per unit time, so I can see exhaust gasses being problematic. Both speak to need for serious ventilation.
I've also heard just having the propane tank inside was risky behavior without explanation of how that's so much worse than natural gas pipes.