I think you misinterpreted what you quoted. Like, nothing you said flowed from the definition you provided. It seems they are saying that 'toxic masculinity' describes men feeling socially pressured to behave in a way that is accepted as masculine even if doing so is destructive to them. They aren't saying that men are innately violent, but rather the opposite, that men are being pressured into behaving that way despite their instincts. Knowing the way teenage boys work because I was one once, I think there is some validity to that. 

I don't know if it is relevant to this case or not, but the concept as a whole isn't crazy unreasonable. You just have to avoid the reactionary knee-jerk when you read about it. They aren't blaming you, relax, they are just hypothesizing how social constructs related to gender might have an effect on a case like this.