I have two things to add:

When you talk about the fact that farmers and oil companies can lose their job, that's not even a argument because the futures market prevents that. Companies that rely heavily on the price of comodities can use futures to offset a decrease on the price of the commodities with the buyer of the product. In addiction, thanks to the futures markets the RETAIL price of rice, corn, chocolate and other commodities doesn't flutuate when you go to the supermarket buying them.

Also, when it comes to short selling stocks, I don't see any problem because retail short sellers entry a trade when there's a "price confirmation" which means the price is already falling and that's when big institutions increase their holdings on that specific company, so they have more liquidity and the spread is much lower.

I think that everyone benefits from short selling. Also, it's kinda crazy that Elon Musk focus so much on short sellers. If I were him, I wouldn't even care about that because the company has a good brand.