Reading around for why he was excommunicated, seems to be a secret. Rumors he was gay though persist:
"Speaking in an interview with the Advocate, Drain speculated that Fred Phelps had at one point wanted to join the military, but suddenly changed his mind.
She said: “All I know is that he said he went to West Point, then all of a sudden he had a religious experience, and now he wanted to preach against sexual immorality, preach against the military, and ever since then things have kind of progressed.”
Drain went on to say that she thought his reaction to being asked by the media if he was gay himself was suspicious, in that it was particularly extreme.
“I never understood why, when [he was asked by the press], ‘Why are you so against the homosexuals? Did you have a homosexual experience? Do you have homosexual tendencies?’ And he would get so mad, he would shut down. And he’d be like, ‘I can’t talk to this person anymore, they’re stupid.’
“His reaction to that was stronger than any other question you can ask him. So I always wondered that — why does he get so mad? If I’m not gay, I’ll just say I’m not gay.”"
Fred Phelps (of Westboro Baptist Protests) Near Death
As to suggestions by some to show up at his funeral with signs reading "We forgive you," when [he whose name shall be forgotten] died we Jews made a holiday out of it, we didn't say we forgive him. What non-Jews do is their business. But G-d didn't ask us to forgive him and make nice. We burn him in effigy and erase all mention of his name. Maybe that's a clue. When...What's his name dies, celebrate his death with a bottle of Jack, and forget his name, but not his deeds or why we hate him. He wasn't our brother, he was evil.