Did fiery essay get author fired?

The Chicago Tribune has a story on "free speech".Allstate fired an employee .J Matt Barber because they didn't like what he wrote on the web.Barber's defense:

The strategy behind Barber's lawsuit is an unusual one, said Matthew Finkin, law professor at the University of Illinois at Urbana-Champaign. Contrary to popular belief, private companies in Illinois and in virtually every other state can fire workers for saying things that embarrass the company--a fact many bloggers have learned the hard way, he said.

Barber's theory is that his views on same-sex marriage constitute religious expression and thus are protected under federal civil rights laws.

The suit is phrased accordingly, saying Barber "felt led of God to write and submit [the article] for online publication."

Free speech is great,what ever happened to the notion of "freedom of contract" in the labor market? Because if there was freedom in hiring and firing we'd never here about this kind of story.