The Internet is bloated with over-opinionated jerks. Everyone knows this; but it's never anything to lose sleep over until someone comes after you personally. If your reputation is attacked by an anonymous online user on Yelp or some other public site, what should you do?
First, take a deep breath. Before you do anything, think about how your reactions will make you appear. Possibly the worst thing you can do is freak out and threaten to sue.