Hi there,
Ugh. That sounds awful. Unfortunately the chances of turning someone like that around are zero to none. Trolling is likely their primary (if not only) motivating force for being a part of the community.
This post will likely be an interesting read. Michael’s video is especially good.
This thread (on my own community) might also be helpful.
Bottom line (in my opinion) is that for the ongoing health of the community, the member needs to be removed. A lynch mob approach is less likely to work than a frank conversation with management.