They're shouting because they're frightened -- truly frightened of the truth about themselves, which is always far more frightening than any fear of what might be lurking outside ourselves in the dark.
The response to that fear is [...] trying to prove to themselves that they are different enough to MAKE A DIFFERENCE by contrasting themselves with baby-killing Satan-worshippers.
With baby-killing Satan-worshippers that they know are purely imaginary. That requires more self-deception than any of us is capable of on our own. That degree of self-deception requires a group.
This is why the rumor doesn't really need to be plausible or believable. It isn't intended to deceive others. It's intended to invite others to participate with you in deception.
