What can I do when someone is using my name in the Gallery to make me look bad?

Someone is posting comments like "Piece of Shite" and "Piece of Crap" as comments on people's bikes in the bike shot gallery.

What can I do? I emailed the site admins but no replies.

Over on mtbr.com they usually block IPs from posting when some does something like this.

Anyone have any suggestions?