The basic reason GNU demands its share in name is bacause of its contribution and its existance far prior to Linux kernal development.
Linux,the kernal, was written and tested using GNU tools.
Stallman is not idiot. He developed GCC by which Linus developed the kernal.
But GNU/Linux is quite long to say nad type.
http://www.gnu.org/gnu/gnu-linux-faq.html by Stallman