This is not a religious liberty issue. The Marine in question disobeyed a lawful order. Marines are not allowed to affix ANYTHING to ADPE (automated data processing equipment) in their spaces. Personal items such as photos or stickers of “Hello Kitty” are also disallowed. Her SNCO and OIC have authority over what items are allowed on desk spaces, providing it does not take up the majority of the space. All Marines are expected to maintain a professional environment and not clutter their desks. This Marine disregarded all orders to the contrary.
That was not the reason given, though. The reason was that the message was “combative,” not that it created a cluttered work space.