Earlier quoted context omitted.
Modern society would collapse if insider trading was legal. It would about as well as making bribery legal.
That's absurd. Insider trading makes markets more efficient as the information enters the market earlier, allowing them to reach the correct price sooner. There's no insider trading laws in commodities or real estate, have those markets collapsed?
How exactly do you think this happens? If I know that a stock is about to rise significantly, I can just buy it at the current price all the way up to the day the information becomes public, and I will not have changed its price at all, but will profit massively off of my inside information.
The market will not reach the correct price until material information becomes public.