At What Point Does Free Speech End?

From Firehouse.com: A former Howard County fire officer is suing in federal court to get his job back, alleging that the county violated his rights by firing him for personal Facebook discussions about gun control, free speech and "liberal" politics.
Former Battalion Chief Kevin P. Buker, who worked for the Howard County Department of Fire and Rescue Services from 1997 until he was let go in March, contends that the county violated his First Amendment rights by prohibiting speech on public issues that did not interfere with his job performance.
Public employees in Maryland have been demoted and disciplined for online activities before, but lawyers who practice in the field said they knew of no similar cases here in which a government worker has been fired.
In a complaint filed last month in U.S. District Court, Buker's lawyers argued that the department "has never identified any disruption to the workplace that occurred as a result of any of Mr. Buker's aforementioned Facebook activities, or the responses to those activities by third parties, and no such disruptions occurred."
Buker -- who according to the county was making $103,659 when he was fired -- is asking to be reinstated and to be paid back salary, benefits, attorney fees and compensatory damages for "mental anguish and distress."
Edward S. Robson, Buker's lead lawyer, said the county made it "very clear" in his termination notice that "the reason they terminated him was because of the substance of his comments on Facebook," not because he was spending time on social media while on duty.
Howard County Solicitor Margaret Ann Nolan said in an email that "the employment action taken did not violate the law; the specific arguments in support of that defense will be set out in our written response filed in court."  http://www.firehouse.com/news/11219998/dismissed-for-facebook-post-howard-md-fire-officer-sues
At what point does an employee's free speech end and job rights begin?
For instance, as the writer of this blog, I probably  definitely would have pissed a lot of my fellow employees in CCSD and many of the my parents of students I work with because of my political views, especially my views against President Obama and NV Sen. Senile/Coward/Liar Harry Reid.
Should I be fired because I put out views that are contrary to the views of my co-workers and parents?  Of course not, unless I cross the line and commit a crime, like calling for the assassination of Reid or Obama, which I never would do.  Wishing that a lightening bolt would strike them is another story....
But then, I don't publically state who I am, I don't put my name in the public, unlike you have to do with Facebook and maybe Twitter.  I don't use those web sites and seeking publicity using my name is one reason why I don't.
This firefighter used Facebook and put out his name to the public, but should he be terminated for this just because of his political views?  Of course not. (Maybe a firefighter making $103,000+ is cause for being fired, but that's another story)
I hope the firefighter gets his job back, if the facts stated in the article are true because freedom of speech is very important, even in 2013.