claus - 8:04 pm on Aug 15, 2010 (gmt 0)
If you plainly remove the whole thread you open up a support issue, of sorts: How are the people that have posted in the thread supposed to find out what happened to their posted wisdom?
Personally I would prefer a manual edit. That makes issues clearer for people to understand, and it also adds a "human touch" to the "feel" of your site.
If that is not possible, I would remove the whole thread, but in its place I would put up a generic message about the thread being moved because of TOS violation.