Your employer can fire you for any stupid thing you say, Tweet, blog, etc.
I mean, unless it's especially protected speech. That is to say, speech which is protected by the National Labor Relations Act.
Posting a Facebook status where you say "My boss is an ass-monkey" can get you fired. But a post that says "My boss is an ass-monkey for not giving us better wages and working conditions" is protected.
"Candidly discussing wages, hours and working conditions" is something that's allowed under the NLRA. So get over it.
Plus, here's a fantasy ninja sword.