I'd never thought about this line of reasoning but it's an interesting hypothetical question. The Wikipedia article on insider trading is surprisingly informative on the counterarguments:
"Milton Friedman, laureate of the Nobel Memorial Prize in Economics, said: "You want more insider trading, not less. You want to give the people most likely to have knowledge about deficiencies of the company an incentive to make the public aware of that." Friedman did not believe that the trader should be required to make his trade known to the public, because the buying or selling pressure itself is information for the market"
...
"Legalization advocates also question why "trading" where one party has more information than the other is legal in other markets, such as real estate, but not in the stock market. For example, if a geologist knows there is a high likelihood of the discovery of petroleum under Farmer Smith's land, he may be entitled to make Smith an offer for the land, and buy it, without first telling Farmer Smith of the geological data.[2] Nevertheless, circumstances can occur when the geologist would be committing fraud if, because he owes a duty to the farmer, he did not disclose the information; for example, if he had been hired by Farmer Smith to assess the geology of the farm."
...
"There are very limited laws against "insider trading" in the commodities markets if, for no other reason than that the concept of an "insider" is not immediately analogous to commodities themselves (corn, wheat, steel, etc.). However, analogous activities such as front running are illegal under US commodity and futures trading laws. For example, a commodity broker can be charged with fraud by receiving a large purchase order from a client (one likely to affect the price of that commodity) and then purchasing that commodity before executing the client's order to benefit from the anticipated price increase."
It doesn't feel that contradictory for me to believe insider trading should be a illegal in equities but legal in commodities, if only because of the externalities involving trust in corporate governance, the conflicting incentives (if the CEO can short his own stock, that creates some perverse incentives). But there definitely a pro-market-signalling argument to be made WRT to the OP's article.