Probably would just be easier to

1) Leave them some negative feedback and encourage others to do the same.
2) Start a flag and encourage others to support it.
3) Add them to your ignore list
4) ~ in your trust list.

And then move on. Is it 100% proper use of flags and feedback. Perhaps not, but who cares. They are here to troll / scam and after a while the person(s) who have been actively cluttering up the lending board will move on. If not, they are just wasting time but at least not cluttering up the board elsewhere.

-Dave