There is a world of difference between playing a game of chance, and playing a game where you happen to believe you have real better/different information about how the future unfolds. Speculators tend to act mostly on emotion and inertia from the game, not any real understanding of any underlying fundamentals.

Short sales can be good. Downward pressure can be healthy. If you think a company is overvalued because its fundamentals are misjudged, the short is a corrective force in an overly optimistic market