The problem is, this analogy is not precise. In patent wars it often doesn't work because there are privateers (NPE patent trolls) which have nothing to lose and MS and other patent aggressors readily employ them to do the dirty work for them in order to avoid retaliation. So, the mere existence of many big patent holders does nothing to prevent such threats, and especially for smaller players.

True - it doesn't reduce the patent threat for smaller players. But it does limit the dominance of any one big player and provide more opportunities for smaller players to participate.