TXHRGuy,
My point was not so much that you legally can't regulate, but rather, you will drive yourself nuts trying to regulate what everyone talks about. Companies for years have had policies about not talking about your compensation, yet we all know it happens everyday. At some point you need to let your employees work it out for themselves.
Your example of being required to say "George Bush is the best president ever" is valid, but once those employees walk through that door and get together at lunch or over their cubical wall, unless you listen to every word they utter, you can't practically stop them from saying "He's the worst president ever." If you hear it can you discipline, sure, but you will spend most of your day running after your employees listening in. Though it does bring up a funny mental picture.