Sorry if I am repeating what somebody might have already pointed out, but owning ANY stock is part of the problem, not just owning stock in a "bad" company. You seem to be interested in doing right by people (e.g. joining the Green party, being ecologically sensitive in stock buying, etc.), so think along somewhat more Marxist lines about exploitation of the worker by capital and you might realize that ownership of any capital, no matter how "kind" or "ecologically sensitve" a company is, still bloodies the hands of the owners (albeit in varying "amounts" depending on how much direct control the capitalist has in the form of shareholding percentage and type of stock). I'm afraid my explanation might be a bit on the light side, so may I recommend a book called Wall Street by our esteemed moderator Doug Henwood (you can pay me that percentage later, Doug).
Todd