How can people make excuses like this for their children?

I always held my children accountable. I never made up excuses for bad behavior. But it seems like most parents are like the mother of this “15 year old who threatened to bring his father’s M15 assault rifle to school and seven people at a minimum.
What does Mom say? ”...he’s just a little kid playing a video game.”
15 is NOT a “little kid.” He may not be a man, but he is not a little kid.