Not much you can legally do.
Its not technically salnder (or in this case libel) either.
Its not libel to say:
"I hate the George Foreman Grill"
It is libel to say:
"The George Foreman Grill is made with faulty parts so that it will explode after a year"
(unless it
is actually made to do so...)
What seems to work is make an email account with
legal@mysite.com and send some letter. The cost analysis of, is this worth it or not, stops most people at this point.