If you don't know who Fred Phelps is, he was the pastor of the Westboro Baptist Church in Kansas and a notoriously bilious gay-hater ("homophobe" just doesn't do him justice) who used to lead his congregation in gay-hating protests at funerals with signs reading, among other things, "God Hates Fags". Phelps is pretty much the poster boy for religious bigotry and extremism.
His passing, whenever it happens, will not end his congregation's despicable work, inasmuch as he managed to accumulate a coterie of true believers whose hate is undiminished. Oddly, though, Phelps himself seems to have been excommunicated from his own church not long ago; it's not clear why.
I'd make a lousy Christian because I find it difficult to forgive those who commit what I see as terrible sins. I wasn't kind to Harold Camping for his idiocies and I think Phelps is much, much worse, he being not a fool but a hatemonger.
It's hard not to be glad he's on his way out and it'll be harder not to cheer when he's finally gone. Still, we shouldn't. Not because it's unChristian (I wouldn't know about that) but because the harm he did will live on through the equally hateful family members who comprise his flock. (Some family members, such as Nathan, have left the church.) However, the world will be a better place without him.