Taking a neutral stance is a tacit endorsement of the validity of the message being spread as being worthy of discussion. Extremism does not deserve its day in court, even if the outcome were a thumping victory for reason and moderation. Besides, the nature of extremists is that they are not amenable to being convinced by reason or argument. Their beliefs are impervious to facts, and that is why debate is a pointless exercise except to give them a platform by which to spread their message, organize, and validate themselves to a wider audience.