I'm going to assume that you're either totally ignorant of Anton La Vey's writings or you're just plain stupid.
The COS and La Vey do not believe in the devil/satan as an anthropomorphic (real) being.
Satan is used to promote atheism because the very image of satan conjures up images of the opposer.
There is NO satan.
It's an idea...that's all.
La Vey chose to use it because he understood the power of symbols.
The christians, being the superstitious lot that they are, are easily riled when confronted with their devil guy.
La Vey used satan to get under their skin and he did a fine job of it.
Of course, there will always be the idiots who will pretend to be 'real' satanists who actually worship the devil.
But they're simply as fucked in tje head as the christians :-)