The problem with this reasoning is obvious: given that "idea patents" are now commonly awarded, these guys are much more likely to be sued by a troll who has already acquired a patent on the idea, than they are to be able to defend their IP by threatening a patent suit against someone else. An eye for an eye leaves the whole world blind.

Patents are no defense against patent trolls, because (by definition) the patent trolls don't actually produce anything. There is no defense against patent trolls, except lobbying to narrow the scope and duration of technology patents.