nobody really has a good idea for how to stop them

That's because they are playing by the rules of the game. If the patent system truly did what it was supposed to do, so called "patent trolls" would be offering a valuable service by providing liquidity to inventors.

The distinction between a "troll" and a "legitimate" company as regards their abuse of the patent system can be very thin. Is it enough that my company provides a patent or service that I am now allowed to sue the bejesus out of anyone with my patent thicket without earning the ire of the public and the label of "troll". It appears so, even if the patent thicket used for such abuse is tangentially related or even not related at all to the product or service actually offered.

People criticising "trolls" recognise a distinction between companies that only exist to sue people and companies that sue people and also offer a product or service, but they never go so far as to question whether the abuse of the patent system by "legitimate" companies can be harmful to innovation in precisely the same way.