I've worked with a number of online communities, and have come to the conclusion that the main reason "trolls" exist is to gain some kind of satisfaction/energy/ego from the responses they can exite - regardless of the content of the response. In other words, any response to a troll is actually feeding them.
We have made it SOP to NEVER respond to a troll, even to say it is a troll, and to delete it if necessary. PM is great at ranking and deleting useless or distracting posts, but I notice an over abundance of responses discussing Troll posts. I bet the trolls would shrivel and die if they never received even a single response to their posts or even a discussion of how bad they are.
Of course it would be necessary to educate new users to this policy.