See the affirmative defenses.

From BusinessInsider.com:

"Propane giant AmeriGas recently sued online complaints forum Pissed Consumer for trademark infringement.

"Gas company executives were presumably upset with how high the complaints page ranks when you search for their brand name.

"Unfortunately for them, Pissed Consumer took the opportunity to make AmeriGas look even worse. In court documents, the consumer forum claimed that users with AmeriGas IP addresses logged onto Pissed Consumer and responded to complaints with 'comments that mock, belittle and abuse.'

"Some of these comments allegedly made by AmeriGas employees are pretty obnoxious: ..."

Read more: http://www.businessinsider.com/amerigas-employees-allegedly-cussed-out-customers-in-complaints-forum-2012-7#ixzz20vup4FUO