I actually find sites for say The Church of Latter Day Saints or Church of Christ Scientist or even sites for the Jehovah's Witnesses scarier.
These satanist churches, you can look at their beliefs and FAQ's and tell that they are teaching a humanist/pantheistic worldview which exists as counter-Christian. Those listed above, make mention of Christ, yet skew their doctrine in ways just enough to make them non-Christian. I have found that most Christians can easily detect humanist or pagan viewpoints which directly counter Christianity. Yet some of the doctrines of those listed above, a number of Christians would consider them just fine.
But hey, that's me.