That name may not be familiar to you, but I am sure his church is. Westboro Baptist Church of Topeka, Kansas.
Phelps and his church had their main claim to fame through picketing and protesting the funerals of soldiers who had died in combat in the US and especially through their hatred of people who are gay and lesbian. They used as a rallying cry the phrase “God hates ____” and used a derogatory name.