It's not that it's less serious, it's that it comes from a different circumstance and affects demographics that many gun control advocates don't actually have any interest in helping.
That could be motivation if one doesn't mind absurdity, like “gun control yes, but you're exempt if you pinky-promise you only shoot <people-I-don't-like>”.
I really don't know what you're trying to say. Is the implication that I don't care about the impoverished black kid that has to grow up in a world with highly prevalent incidental crime-related gun violence? If that's what you're getting at, please re-read my previous comment.
This data was compiled with the criteria it was to inflate the perceived number of "muh assault rifle" headliner-style school shootings. You're probably never going to turn on national news and see any reporting on any of these crime disputes that came to a head at/near a school. There is very little political willpower to do anything about these instances and not calling this shit out for what it is is a disservice to the people that are actually impacted by this strain of gun violence.
EDIT: after re-reading your comment a few more times, I think what you were trying to say is that it doesn't make sense that people would overlook some gun violence and worry more about other instances, but I've got bad news for you -- they do it all the fucking time. It's not that it's <people-they-don't-like>, it's <people-they-don't-think-about-at-all>, save when they make for a convenient data point.
My comment wasn't meant as an attack on you, on the contrary. I think we agree on your points. I find it absurd that one can be pro gun control but then be selective about what kind of gun violence it's meant to reduce.