I don't think we disagree. You don't like the company you work for? You Quit. You think it's not the company you joined some time ago? You Quit. I can go on and on like this. You didn't promise to increase shareholder value, but you did promise you would try in good faith.

None of this justifies willfully harming your employer.

Edit: One of the things that is an exception I believe is whistle blowing. You may expose stuff you deem unacceptable or harmful to the general public. But I guess that's about it. Of course this all depends on your jurisdiction.