There are (at least) two meanings of "stupid" floating around here, morally stupid and commercially stupid. dcurtis seems to be thinking of commercial stupidity, i.e., "no one will ever buy/use this", but you're thinking of moral stupidity, or "this idea, if executed, will make the world a worse place."

They're not strongly correlated. Cigarettes are commercially smart and morally stupid. Charities, in some sense, are morally smart and commercially stupid, assuming they do good for the world and don't make a profit. As entrepreneurs, ideally we'd like to find something both morally and commercially smart.