As a follow-up to my post earlier this week, an op-ed appeared in the L.A. Times recently that gives a good summation of what kinds of expression can and cannot be limited without violating the First Amendment.
The author of that op-ed is a lawyer whose blog, Popehat, I think I have linked to in the past. He occasionally writes posts about First Amendment cases that are worth reading.
The contents of this blog, this web site, and any writings by me that are linked here, are all my personal commentary. None of it is intended to be legal advice for your situation.