I have been engaging in a discussion on twitter about whether the Santa Barbara killer was a terrorist or not. My basic starting point is: is the violence aimed to produce a political effect? Or it just aimed to kill people? Perhaps all violence is political, but I tend to see terrorism as an effort to alter a political context--to cause a government to overreact and over-reach (9/11), to compel a government to bargain (terrorist kidnapping, for instance), to spark/inspire a political movement, and so on.
There is apparently much twisted stuff in the misogynist's manifesto, including reference to ideology. He apparently did associate with those who shared his sense of grievance, focusing strangely enough on those tricksters that promise to offer tips to pick up ladies.
At this early juncture, I don't think this guy is the Timothy McVeigh of the misogyny movement. But it is early.
Why does this matter? As a non-expert on terrorism, I would still think this has practical implications and not just an academic exercise. If it is terrorism, then that affects how one thinks of prevention and of response. If it is just a crazed individual trying to go out in the most spectacular way possible (was Columbine terrorism? I don't know), then one does not have to trace who supported the effort, who benefited from the effort, how to diminish the "spark", and so on. If it is terrorism, then governments would want to do serious work to reduce the impact, deal with any networks of support, and perhaps even engage in information operations (propaganda) to offset the messaging.
Of course, I am just spitballing since I am not very well read on this stuff, and I only teach a week or so of terrorism in my Contemporary International Security course.