I can't see a need for it. As for taking away their right to do it, absolutely not. I wouldn't want to and I couldn't even if I did want to. They can say what they like but it's hardly a wise thing to do as far as I see it.
First off lets have a look at what you are trying to do when you debate something. I think you are trying to get your view across and bring the opposition to your way of thinking so insulting them is not a good way to do it.
How much better to say,"well I think you are wrong, because", rather than " You idiot", or whatever. So do you think it's o'k to insult people ?