That said, I have seen a lot of anti-Mormons refer to it as some sort of proof that the church produces crazed serial killers. IIRC, it is based on the Lafferty Brothers. They basically went insane and killed some people, claiming that they were doing it based on revelation.

IMO, their membership in the church may have led them to believe the voices in their heads were revelation instead of whatever they would have believed otherwise. But, again IMO, they would have killed regardless of their membership in the church. Any group that gets large enough will have its nutjobs.