Surely, putting forth a better argument or, at least, ignoring them is a far more morally superior response than suppressing their speech?
I've recently read about Bobby Sands (who was a IRA member who starved himself to death) and am reminded of that monk who lit themself on fire in protest.
I think an interesting question about these two people is why did their action have any impact? The authorities were against them and killing themselves doesn't "oppress" those authorities.
I think the opening paragraph of this book http://www.jstor.org/stable/3750951 is an interesting angle: martyrs against a cause illegitimize a cause.
If that is true, as I think it is, then it is crucially important to not victimize people no matter how wrong they may be. I think that the way to do that is, as I said above, to tolerate wrong viewpoints but respond to them or ignore them.