The difference is that the people selling the thing want you to lose. They're the counterparty. A real broker doesn't care. They just get a commission on the trade either way.
That is not a difference from either the call option model or the short sale model. It's true in all "three" cases.
Furthermore, if your intention as a rope vendor is specifically to sell someone enough to hang themselves with, you're not operating a scam as you sell them the rope.