Under what regulatory regime is a corporation able to rape the environment and siphon off the money? Who says that corporations as they exist today should exist in libertarian-land? Perhaps you'd have only LLCs where the limitation of liability is actually rather small and as such management would take an active role in ensuring that they weren't personally liable for the rapacious behavior that some corporations exhibit today.

Up until Glass-Steagall was repealed Goldman-Sachs was a relatively well run bank that was entirely privately owned and all the partners there made sure people weren't doing crazy subprime stuff because it would negatively impact the bottom line over the next decade or more.

Nassim Taleb talks about "skin in the game" as a requisite for moral decision making. Perhaps libertarians would say that you can't perform in a managerial role at a company without having some meaningful skin in the game. Would people find a way to dodge that? Sure. But companies who did dodge it would tend to be short-term greedy, not long-term greedy and as a result they would tend to go bankrupt faster thus ridding us of the unpleasantness of their existence.