In this age of political correctness, what was once a cute thing (cutting off someones tie) could be thought of as harrassment and assault and if the patron wanted to push it, could result in the arrest of the bescissored waiter.
I hate ties and try not to wear one, but if I were in this situation, and the restaurant had a no-tie policy, I would just take it off when asked. If someone tried to forcibly remove it, well, lets just say that I would not be pleased. In fact, if it was an expensive tie, I would insist on being reimbursed for the cost.
As for Adjudicators comment,pulling out a gun may be taking it a little too far, but Michael Hoffman is wrong about only a criminal doing this. I think most courts would agree that holding an open pair of scissors at your throat could in itself be construed as assault with a deadly weapon, in which case another deadly weapon could be legally used for defense. As for V960's remedy, well, what would you do if it was a waitress instead of a waiter.