We know that we can't negotiate, reason with, or cajole the zealots of Al Qaeda - thus, there must exist some line where people cross from being those we can and will hold intelligent dialogue with, and those that we simply must shun. When those we shun step over the line to illegality or revolution - then we must fight.
There are pragmatic conservatives that recognize no one has a lock on truth - these are people we liberals and progressives can readily negotiate and compromise with. But there is also the self-righteous rabble on the right that is similar to Iran - theologically and ideologically oriented rather than pragmatic, and hence very difficult to talk to or negotiate with when you don't share their theology or ideology. Nevertheless, engaging them is a necessary (albeit Sisyphean) task.
Beyond this difficult and frustrating group on the far right, there are those fringers who are as closed-minded and medieval as our terrorist enemies. Just like those inspired by Al Qaeda, those inspired by the righteous rabble have struck here (remember Oklahoma City? how about the murders in the name of "life") For those on the self-righteous fringe, I think shunning is our best option. Until they act on their calls for revolution and armed insurrection, we really can't do much about them without becoming the type of tyranny we despise. To hold up our liberal ideals, we can only react. Pre-emptive action without proof of illegality is the start of tyranny.
I certainly have no problem shunning the left-wing ELF, the environmental activists who have endangered people with illegal acts, or the anti-globalization protesters that have organized riots around the world. I think that we of the left have been very careful in criticizing those who do violence in our name, but have been too forgiving of the crazies on the right.
Those that march on the people's elected government with signs such as "next time I come armed" are people we cannot reason with. They are dangerous. We can only shun them, watch them, and hope for the best.
The above was inspired by...