Why do atheists assume that Satanism is an atheistic religion?

http://en.wikipedia.org/wiki/Theistic_Satanism

They are two form of satanism. One where you do not believe in Satan as an entity and one where you believe in Satan as an entity.

Didn't know atheists had a religion.

I don't...then again, I don't spend my time researching Satan...

The atheistic form of Satanism is the one that Satan himself conjured. The theistic one was made by sinful humans.

Atheistic? Is that kinda sorta not maybe believing in a Deity, God or Satan?

There are two forms in which I care:
1) Not at all, couldn't care less.
2) I don't give even the slightest turd.

Source or citation, or STFU.

Atheists are very hypocritical. They say they have no religion and believe in nothing but then they go into satanism??

WOE to the Inhabitors of the Earth!

You have LaVey Satanism and traditional Satanism.

Simply put, traditional Satanism reveres Satan as lord, and God exists.

LaVey Satanism states that there are no gods other than yourself, because you are the creator of your own purpose and destiny.
The name was chosen purely for shock value.

couldn't care less about what they bollixed

Good question - one surely Prue-supposes the other. Although how someone can believe in satanism and not believe in the entity is a puzzle.

And the other puzzle is why is it that a person who believes in Satan and consequently Prue-supposes the existence of God then chooses Satan instead of God. True atheists of course don't believe in either.

Yes, I knew that. LaVeyan satanists are atheists and Theistic satanists are devil-worshipers.

It's a form of symbolism via rebellion against Christian-related religions, this is often misinterpreted as "satanism" when it's merely anti-theism.

Because theistic Satanists are a tiny minority of all Satanists. The vast majority today are LaVeyan Satanists. LaVeyan Satanism is explicitly atheistic.

And also because, in the long history of paranoid Christian claims of Satanism, and their persecution of people who were accused of it, no authentic examples have ever been produced. Even in the article you linked, there are statements about what such Satanists believe, but none are quoted as doing so.

Even the groups named are not rightly called theistic Satanists, but LaVeyans (atheists) or Noe-pagans. Some of them espouse the "left-hand path," but that isn't the same thing.

There are actually four main forms of Satanism, only one of which is atheistic.

Both are cults of Christianity since Satan is a christian entity whether you like it or not!!

Actually, there are a lot more than just two kinds of Satanism.

We don't. The only one that is making assumptions here is you.

Satanists ARE atheists. I should know I know enough of them and have read their books

Why do you assume that I do? I have known for a long time there were various types some theistic as well as the generally atheistic Church of Satan.