This boy needs to clean the latrines with a toothbrush for a few months
While I understand your passion and I respect the First Amendment, please understand that I don't tolerate activity that gets in the way of your or others productivity.
That being said, you are warned that if your political activism in the workplace continues, it will only continue with you in the role of a visitor to the company, and you will therefore be limited to either the breakroom or parking lot to continue talking with anyone who wants to listen.
Is this job in an "at will" state? If so, he can be terminated and given no reason. Just don't give an illegal reason such as sexual preference, age, etc.
What would your position be if it were a left-wing business owner (there are plenty) and an employee who was an active Freeper that posted on company time?
If you are creating an atmosphere that is making it difficult for other people to do their work then I will fire you. And I dare you to try to sue me. The posting on the Internet is one thing, although if he in not doing it during break time and it is excessive then I would have a chat with him, as it is an activity that you can do without bothering anyone else. However, picking fights with coworkers, or saying things to annoy and harass them is simply not acceptable.
Oh, by the way First Amendment Rights does not mean that you can say what you will at work, it simply means that you will not be arrested. Fired is quite another thing.
Cruising the Internet can expose the computer (yours) and the network (yours) to viruses, backdoor trojans, hijackers, spam, porn, and insidious worms that can do great damage to your productivity and your business. Warn your employees and then have your IT professional check the traffic. If you don't have an IT policy yet, draft one and implement it with fair warning. It is grounds for termination, if he understands the policy.
If he is pestering other employees by sending unsolicited email and attachments, that is another matter altogether. To allow this to continue could open your business (and you) to a lawsuit for sexual harrassment. (Even if the content is political, often there is a pornographic element to it.) He MUST be terminated, in that case, no warning necessary.
Just make sure that you document the infractions.
I've been there. I overlooked a salesman's cruising on the Internet because I do it too, but it took me 12 hours of work to rebuild a his computer after he was fired for not doing is job. And I still haven't gotten all the junk out of my network.
Backdoors and highjackers are all over the Internet and can wreak havoc with your company files -- even if there was no ham intended. When your computers slow to a crawl, youwill know what I mean.
Read teh whole article. The advice offered by Business Week is good in the first sentence and then it degeneratives into a bunch of touchy-feely pap, such as "work out a compromise among the employees." Gag! Anyone who endangers my network around here is out the door!