The man who shot Giffords was certifiably mentally ill. Even the Huffington Post at the time recognized the connection to mental illness. (http://www.huffingtonpost.com/dj-jaffe/gabrielle-gifford-jared-l_b_806279.html)
Before that shooting, Giffords was energetic for mental health care reform. How much has Giffords agitated for mental health care reforms since the shooting? (hint: zero).
Why no mental health reforms that would get them into treatment and keep guns out of their hands? Why no reforms of the Watch List that would enable keeping guns out of the hands of people on that list? Why are convicted felons who are in our country illegally released back into our communities rather than deported? There are reasonable steps that can be taken with support from both sides; why aren’t they?
Because it’s so much more fun to hold a sit-in in the House of Representatives. The issue is so much more politically useful than any solution, and Democrats are loathe to give it up.