I've come across a couple of his post over the past weeks, and I initially though s/he was someone you could reason with and discuss factually, I've long been proven wrong.

Best option is probably to put the account on ignore.
Restricting such FUDs in any form, would spark another kindle of FUD. Directed against the forum, and how it's against criticism.

No-one genuinely interested in bitcoin should be much deterred much by such FUD as they are everywhere and we can't control all of it.