No offense (and I'm not biased either way) but not looking at the short side is like always betting on red at roulette. Stocks go up and down based on a slew of factors, and the objective is to make money. So if you come across something that is negative, you bet black instead of red.
Its not un-american, and usually does not hurt the company (unless of course you turn out to be right, and then its usually their fault anyway), unless you are an institutional investor with large size positions.
It's easy to be optimistic all the time, but there are lots of poorly managed companies, and lots of bad products. It takes a bit of extra time to do the research (since Wall Street will always help you buy things), but some of my best long-term investments have been in companies that had fundamental business plan flaws and went away. My bias has always been long, but a portfolio that is beta ajusted with both longs and shorts takes a lot of the 'market' out of the portfolio, and lets the fundamentals do the talking. JMHO.