There is precedent that protects web site operators from comments by it's users BUT you must speak with a qualified attorney to understand everything you must do in order to have them apply to your site.
You should be able to inexpensively add Errors and Omissions insurance to your business liability which can help protect you from claims arising from this...even frivolous claims.
Disclaimer: The contents of this post are for informational purposes only and should not be construed as legal advice. I am not a lawyer, so I do not give legal advice. If you should have any questions or want professional assurance that the information is appropriate to your situation please consult a licensed attorney.
