In fact my employer can muzzle me. I've signed various documents over the years that prevent my from speaking about my employer (or past employers) in various w

In fact my employer can muzzle me. I've signed various documents over the years that prevent my from speaking about my employer (or past employers) in various ways. And the fact that my employer can't have me beaten up has nothing to do with the 1st amendment. That would be assault no matter what their motivation.