Yes, shorting is a possibility. However, it can only be done on paper. Sure, it might influence the price somewhat in the short term, but it can't be sustained forever and making bitcoin cheap is not anyhow suppressing its main fundamental features, the main one being not controlled by anyone in any meaningful way.
Discussion
I'm focusing more on how this is the mechanism to keep the price of Gold down. No one at the big banks or the gov't will ever talk about the huge short positions against gold that's on their books. No one, of course, will tell you who gave the orders to put the trades on. In one of the articles I posted, it seems Germany had 20 times their GDP in gold shorts. If they had to buy gold to cover, how high would gold go? But they don't. They keep rolling out on expiration dates. They don't want to go near physical gold.
Yes, physical gold is definitely being manipulated heavily. Bitcoin on the other hand due to its properties is much harder to manipulate in the same fashion, if not impossible at all.