Recognize that most trolls do it because they love to see their words on the screen. Many go to great lengths in constructing their posts. Here's what we do:
First time: We ban 'em
Second Time: We mass delete their posts. They get a simple email explaining that, while it may have taken them several hours to generate their 96 posts, it took the system 30 seconds to delete every word they ever typed.
This tends to take the wind out of their sails. As has been pointed out, you can't allow them to believe it's become personal. They need to understand that dealing with Trolls is a simple exercize in your normal admin duties.

YMMV
Rich