This country has changed since 9/11. And the high powered rifles that enabled the extremist fueled act of terrorism in California are just one ingredient to a perfect cocktail that includes all that's ugly in America today.
The uncomfortable truth is that essentialized conceptualizations that say "Islam = violence" or "Islam = peace" are insensitive to the alterations and negotiations that characterizes lived Islam in interaction with myriad Muslim constituencies and non-Muslim actors.
It seems like Americans, from Faisal Shahzad to the Hutaree Christian militia group, are addicted to solving problems by the violent marginalization of individuals and groups. And they sure do like their weapons.