nycnitte,
I presume a "valuation long" is buying the stock and holding it. That's an assertive expression of optimism.
A short is an assertive act of pessimism. It appeals to a sense of fear, not hope. In politics, such acts--in the form of negative advertising--work very well. As a species, we are wired to respond to fear quickly; we show more variation in how (and how quickly) we respond to hope. If fear works in politics, why doesn't work in markets (i.e., valuation shorts)?
I wonder if its that many participants are valuation unaware. Also, accepting that fear has costs to those holding a stock--they may not sell--so, a valuation short may not work out.
Karl