Nope...no more than if an employee were offended by what was in the N. Y. Times. The company did not pay the employee to go surfing "hate" sites....
Remarkably, that's not a defense. The legal problem for the company is the "hostile workplace" action, not the fact that surfing while being paid to do work is in effect stealing from the employer. No kidding, that's really the law. And just try to discipline or terminate the offending employee -- you gotta be ultra-careful about how you do that, too.