>Insiders often also have power over the behaviour of a company, so for example a corporate leader might short his company's stock and then take actions to ruin

>Insiders often also have power over the behaviour of a company, so for example a corporate leader might short his company's stock and then take actions to ruin the business. Or they might release plans for some action that would be seen negatively in the market, depress the stock price, buy, and then change the plans to ones that will attract investors and pocket the difference when the price goes back up. Legalising insider trading wouldn't legalise such behaviour per se, as such behaviour would still constitute a breach of the leader's fiduciary duties. Look for instance at how Musk was prosecuted for doing that kind of thing; such prosecution was unrelated to insider trading laws, and could still occur without them.