I'll just pull the pin and throw this grenade into the room...
The proposed AR-15 ban is idiotic, and ignores deeper problems.
First, despite what recent events may lead you to believe, it is not the 'preferred weapon' of domestic terrorists. The Columbine massacre was accomplished with a Tec-9, a carbine, and a pair of shotguns. The Oklahoma City bombing was acomplished with fertilizer and other easily obtainable chemicals. The 9/11 attack was accomplished with planes and box cutters. and did not involve firearms at all.
Second, there are any number of weapons that can sub in for an AR-15. I'm reasonably confident that if I wanted an AK-47, I could get one for somewhere in the range of $500, possibly much cheaper.
A ban would be functionally useless. We should concentrate instead on the complete intelligence failure that allowed someone being monitored by authorities as a dangerous person to 1 get a job as a security guard, and 2 own a weapon at all, let alone an AR-15.