It is one thing for an anti-gun Congresswoman to be shot in the head. (Not justifying this obvious breach of just war doctrine, but perhaps AZ is not the ideal place to establish a beachhead for progressive gun control.) In a free society, it is always a risk that an enraged lunatic will take the law into his own hands, attempting assassination–whether by gun or knife or bomb or bare hands. Happens all the time with knives, in fact.
But for TWELVE (including a child) to be injured (not sure yet how many fatalities)–that is just inexcusable, and those attending are to be blamed for not defending themselves. I doubt very much the carnage would be so great if this had happened at a Republican event attended by a people trained to bearing arms. The idiot would have been lucky to get one shot off.
These people obviously had too much faith in the ability of law enforcement to protect them.
When you decide not to defend yourself, you put others at risk. Possibly, you put a whole society at risk.