Most of the character flaws of Fred Phelps have already been pointed out.
1) His "church" consists of his own extended family.
2) He seems obsessed with sexual sins.
3) The "blurb" from his church description
"insists that the doctrine of grace be taught publicly to all men", but Phelps "preaches" God's damnation and never mentions His Grace.
There are many more that could be listed (such as the consuming hatred that blots out the common decency to allow family and friend bury their loved ones in peace), but it's all been said before.
As Cloudy mentioned, Phelps is
not representative of the Christian Faith and the Teachings of Jesus Christ by even the wildest stretch of imagination.
I like Ilumina's idea of protesting Phelp's own church services, but this would probably just add fuel to his fire of hatred that is already burning out of control. Still, I think having LAMDA return the favor at Phelp's funeral would be a just and fitting tribute.
