Shorting may exacerbate a move up or down.  But who cares, it's a (somewhat) free market.  People should be able to buy or sell freely.  The advocates of this in this country say that let's do it "just for a little bit".  Let me ask you this, Mr. Short Sale banner guy, how would you like it if BUYING was banned "just for a little bit".  Doesn't make a lot of sense, does it?  So if anyone is trying to convince you that short sale banning is a good idea, ask them this question.  You'll likely get a hand in the cookie jar or deer in the headlights type look.  Ask them to please go back and take their seat ... you've got some stocks to short.  

And for the record, I don't short, ever.  If there is any bias in these markets, it's up.  Maybe not today, but long term, you've put the odds against you.  Trading and investing is hard enough, so why make it harder.  If I'm bearish on something I always use a bearish option play, but I never short a stock.  I still defend your right, short seller, to do it.