"what other limitations do you think apply...?"
Public speaking from within a country in which we are engaged in an armed conflict crosses over the line in my opinion. You can criticize our government and it's policies all you want, but when you do it from an enemy's soil, it's giving aid to the enemy.
Think about this: Do you believe giving a monetary contribution is a form of free speech? If you answered "yes", would it have been fine for Hanoi Jane to send a money to the North Vietnamese Army?