In Neuromarketing's post Damage Control That Causes More Damage they suggest that the best response by PR when confronted by an inaccurate accusation may be to respond positively.

Neuromarketing quotes a study that finds that when people put out information correcting a false statement, it can have the counterintuitive effect of reinforcing the original false statement.

Their advice?

"...the best approach to damage control may be to emphasize the positive. Instead of repeating a rumor that your noise-cancelling headphones cause brain cancer, emphasize their safety and the extensive testing that confirms that.

"..if a rumor or other attack gains so much traction that it’s major news, denial will be necessary. In general, though ... avoid repeating false facts whenever possible..."