Insider trading is not about fairness, it's about theft. If you insider trade on the stock market then, in a crude simplification, you steal profits from the company you have a fiduciary duty to, or some extension of that. It has nothing to do with a level playing ground, every trading company out there is trying to find information others can't and then trade on it.
What? How do you figure that? If I happen to know that my company is about to report very bad quarterly numbers, so I sell all my stock, then it tanks, I’ve just screwed whoever bought the stock, that in the most cases, will be some random people. The company does not benefit or hurt from stock prices unless they are buying back or issuing more stock.
Because that's what the law says? And the company most definitely does benefit and hurt from a fluctuating stock price, it's one of the key drivers behind financing conditions. What you describe is a simpleton view of the financial market.