Ideological partisans of all stripes face this temptation every day — the temptation to believe that those who seem to be making the same argument you make but then add violence to the mix only do so out of an excess of zeal. In other words, the violent people may be wrong in their tactics, but their passionate loathing of injustice simply got the best of their good intentions.

Perhaps they feel it necessary to do so because they don’t want the bad behavior to discredit their beliefs, or because they can’t bear to examine their ­beliefs in light of the violence and wonder if they are a part of what made the violence happen.

Or they double down and come to think that the violence is a mark of virtue — that the ­violent are even more committed than the cowardly couch potatoes who sit on the sidelines bemoaning injustice but refuse to put it all on the line. That was also the story with the cop-killing and bank-robbing terrorism by the Weathermen and others that erupted from the anti-Vietnam-War student protests.