foible

As a simple addition: if you're so magically, supernaturally good as a trader that you know the stock will drop, then by shorting, you are depriving someone from their potential profits. So if you think you're God, you shouldn't trade. Speaking personally, if you think you're God, I would like you to trade. To ease your conscience, why not tell me what you're trading so I can take the other side.

Trading in general is amoral (setting aside hostile takeovers, pillaging companies, stock scams and the rest). You buy from people that want to sell, and you sell to those that want to buy. Your actions have no impact on the company. If you want to hold stocks for longer terms and don't want to get all icky by associating with tobacco, for example, then remember that shares tend to be a net loss to companies as they pay out dividends. The money raised from a public offering is a one-time affair, and after that the shares just drain money. By holding shares, you are taking money away from a company you don't like. Maybe that eases your conscience. (Of course no one cares who holds these shares and you know someone will, so we come back around to trading being amoral )