I agree with Drivin. Also, don't forget that the vast majority of shares are being traded algorithmically. The algorithms don't have a bias or spread FUD, and they will snatch up dips and sell peaks as necessary. I built them and for more than a decade, they took long and short positions. I had no sentiment about the companies I traded, and neither did my algorithms.
As a human trader, there are valid reasons for being short - you have good reason to believe a company is overvalued, or that there are macro conditions that are likely to affect certain segments more dramatically. These don't mean you're unethical.
I feel there's a reason people equate short and unethical, though. Short implies pessimism - not always about the company, but certainly about the valuation. Long implies optimism across the board. Nobody likes a pessimist, especially when they're right.
And as a last thought, I think "real" shorts, the ones who have positions that matter, don't give a damn about spreading FUD or posting on message boards, because they know that isn't going to make a dent in an issue with a ~ $20B market cap and 120MM+ outstanding shares.