WBC isn't a "church", per se.
It's an elaborate cult started by Fred Phelps, Sr. As far as I know, he is the only member who actually believes their message. With everybody else (his wife, kids, etc.), the message was literally beaten into them. Phelps Sr. was very abusive to his family, resulting in four of his kids leaving (and being disowned by him), and the mysterious death of a woman who was briefly married to Fred Jr. and then dating Mark (one of the sons he disowned). If anyone in his family followed a life path different than the one Fred Sr. ordered them to follow (school, law school, joining the family law practice, etc.), they were disowned. The level of support for him by his family measures only how much they are afraid of him, and their only duty in life is to cater to their dad's every whim. His sermons only cover passages in the Bible that support his ultra-far-fetched idea of what the world should be like. Members are not allowed to marry anyone outside the congregation, resulting in incest in some cases.
They believe that they are the only true church, any other pastor is a false prophet, and as such, they are the only ones who will ascend into heaven.
The pickets are not designed to preach the word of God (rather the word of Fred), but to purposely incite some sort of reaction that will give them reason to sue, and thus make money for themselves.
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