Legal question about unwanted endorsements

Let’s say someone who’s almost universally hated, like the “God Hates Fags” guy, Fred Phelps, has a problem with a certain business and tries to get revenge on them by endorsing them on his website to make them look bad. If everything he says about them is factual and/or positive, can they force him to stop? If so, how far can he legally go in drawing attention to them on his site?

My WAG is that the business could make him remove their image, logo, name, and other copyrighted material.

Dunno if they could make him remove a link, though.

-David