Yes, Satanism is an officially recognized religion in the Army...there used to be a Satanic chaplain! He was a Colonel. I saw him on a Geraldo special on Satanism back in '88 - '90 sometime. I had a problem with my squad leader when I converted my religious preference. He tried to bar me from putting it on my dog tags until our EO NCO told him it was legit & he couldn't stop me. He still asked me not to wear those tags when I jumped...of course, I wore them anyway!
Hope this sheds some light on the subject for you.