In the stock market, there are various ways to invest your money such that if a company's stock value goes down, you make profit. In effect, you're betting for these companies to weaken or fail.
Do you think that making such bets is ethical? I'm of a mixed mind.
It's not betting that the company is going to fail, so much as betting that the analysts are wrong. A company doesn't "evaporate" value in relation to a stock price -- there is a value of stock and an actual value of the business in terms of contracts, property, people, and other resources and they rarely coincide at all.
Let's put it more simply:
If you know the stock will decline you short it. (That's to say you make money went it loses value)
If you know the stock will gain you long it. (The exact opposite)
If you only play half the time (when it gains) you only make half the money... Presuming, of course, you were able to accurately determine either case with some consistency. This is why stock investors generally do both -- they may absolutely love a company and root for it in the long term, but they see a short term downtrend and still want to make that money. It's nothing about ethics.