I'm guessing you're serious here, but that's a very unsupported position. I'm for it because it's getting the market more towards perfect information. By them using insider info, stock prices adjust to this information - which is more accurate than without. If you're not sophisticated, that still means the prices are more reasonable. Yes, that means some make money, but that's the cost of a smoother market.
Also - computer trading would be able to pick up to differences in trading strategy (by seeing big positions taken) and react quickly - minimizing total profits and bringing prices closer to reality.
Also - your company would have a higher incentive to treat you well if you could legally sell the info to Goldman Sachs to trade on and give you a commission. That's the populist side of insider trading.
I was only half-serious, but I'll elaborate it into a serious argument anyway.
Allowing insider trading will create asymmetric information in the stock market, and that risks creating a "market for lemons" type situation and reducing liquidity. Say that insiders are allowed to trade whenever they want, on whatever information they have. As an outside investor without that information, I should then assume that I will get a raw deal on any trade that I make. The rational action, then, is to avoid trading that stock at all. Even if there're initially lots of non-insiders to trade with, they are all making the same economic calculation, and will come to the same conclusion. Hence, anyone rational will leave the market, and the only people left will be those with inside information, creating a self-fulfilling prophecy. That defeats the whole point of a public stock market.
When you think about economics, you can't stop at first-order effects. The immediate effect of insider trading may be to increase the speed with which information gets to the market, but the long-term effect is to destroy the market itself, as every participant then has an incentive not to trade.
Anyway, the ironic part of my original comment is that I'm actually not an outsider by most people's POV. I can think of a number of people that would pay good money for upcoming Google product releases, were it not illegal (and grounds for firing). So in strictly personal terms, I'd stand to benefit quite a bit from legalized insider trading, but in academic terms, it'd destroy the system that generally works pretty well.
The problem with insider trading is it leads to stock manipulations which is the opposite of your argument. Pump and dump is possible outside a company, but when you get to write the prospectus there are many more options to mess with the market.
There is nothing illegal about making a company look worse off than it actually is. Couple that with insider information and you can short a stock then release overly pessimistic information. Worse yet, you can decide to delay a product's release for the same effect etc.
Think: Pfizer is considering pulling Viagra from the market in response to a possible side effect. then next week After, a full review we find no evidence that any such effect exists.
Also - computer trading would be able to pick up to differences in trading strategy (by seeing big positions taken) and react quickly - minimizing total profits and bringing prices closer to reality.
Also - your company would have a higher incentive to treat you well if you could legally sell the info to Goldman Sachs to trade on and give you a commission. That's the populist side of insider trading.