For a very good reason.
Unlike truly random attacks, the Islamic terrorists aim at maximizing Christian deaths. It is for this reason that the "holiday" party was targeted - the killers could be reasonably sure that those of the Christian faith would be present. Other groups that have faced terror from Islamicists are the Kurds, the Druze, and, of course, every whacko group's fave, the Jews.
The Progressives have been wrinkling their foreheads at the perplexing actions of ordinary Americans, who - despite the number of shootings by random crazies and "Peaceful Muslims" (trademark pending) - are reacting by choosing to increase the number of guns owned by citizens. It's "truly a puzzlement" (to quote the King of Siam from the musical) why any sane person would react to the increasing violence with purchases to defend themselves and those they love.
I personally know 1/2 dozen or more Democrats who've either bought guns, or are contemplating a purchase.
Whatever COULD be causing people to feel unsafe?
Why, it's as though these nervous people don't fully trust their government to protect them.
They must be paranoid.
[UPDATE] I know it reads like an Onion article, but apparently the appropriate response to the CA shooting should be attendance at a radical mosque:
A handful of House Democrats are expected to meet Friday afternoon at a Northern Virginia mosque that has reported ties to terrorists.
The Dar Al-Hijrah Islamic Center in Falls Church is where Anwar al-Awlaki, an accused recruiter for al Qaeda who was killed in 2011 by a U.S. drone strike, was an imam at the time of the Sept. 11, 2001, terrorist attacks. It was also widely reported that some of 9/11 hijackers attended the mosque, and that Fort Hood shooter Nidal Hasan worshipped there
Have we morphed into Bizarro World?