> Terrorists don't go around killing people for banning them from forums.

It seems incredibly arrogant to assume that you know what terrorists will and will not do (especially when used as a rebuttal to someone expressing concern for real people who have been put in this situation).

I don't have any experience interacting with terrorists, but growing up in a poor education system in the southeastern U.S., I've witnessed my fair share of gang activity. I have seen incredible confrontation/violence erupt as a consequence of amazingly trivial actions.

It does not seem far fetched to me that an extremist group would possess the potential to respond dispraportionately to a perceived act of disrespect or aggression. Given the circumstances, it's hard to find a charitable interpretation of why you would suggest otherwise.