Except when it undermines the human spirit and efforts for a more just and sustainable world. Then it is simply greed, and better opportunities are lost. I would suggest shorting some stocks/companies that have consciously opted for putting greed above sustainability and human life - such as VW, DOW/Monsanto, and fossil fuel industries. In those cases shorting can help accelerate change towards a better future.
While I agree in the principles, I tend to be practical in understanding that the market is a greedy place.