I've scrolled over all the posts in here merely skimming them and not reading them because I can imagine the back and forth. Here's my two cents:
Regardless of whatever rhetoric the shooter was fed, in the end, the decision to kill rested with him solely.
This does not mean that hate speech isn't despicable. Invective moves people away from rational thinking into emotion-filled responses which further entrench us in our allegiances minimizing the opportunities for healthy debate and effective compromise.
We need to stop being assholes. The people we disagree with are people, just like us, albeit with different ideas on how to accomplish surprisingly similar goals. Let's not forget this and treat them with the basic respect they deserve.