That is a poor analogy.
A better one would be this: do you have the right to strip search an employee and rifle through her purse in order to determine if she has written anything insulting to you which violates your "company policy"?.
Was the employee advised of this company policy prior to accepting the job?
If they were, then the company has the right.
The employee exercised their rights at the moment they made a decision on whether to accept the job under those conditions or not.
KoRn's is not a poor analogy at all, it is the perfect analogy.
You don't have a Second Amendment right to carry a gun on to my property against my expressed wishes anymore than I have a First Amendment right to deliver a Muslim service in your yard against your expressed wishes.
Sadly, that's becoming the case in most places, but that's the employer's right as long as you are on company property. If you don't like it, go work somewhere else.