I wouldn't completely dismiss it because it's likely a contributing or aggravating element. Certainly not the main reason though.
Elliot Rodger talked about being rejected my women in his manifesto. The Santa Fe shooter targeted women he who rejected him. The VT shooter had issues with rejection and stalking women.
I may have been a bit too premature with that statement, fair enough. I suppose I'm also associating it with what JP's solution would be - to have a harem of women forced to satisfy undersexed, weird dudes.
As far as male mental health goes, I'm sure addressing it more proactively could help, as well as having a conversation amongst ourselves that women do not "owe" you something - regardless of your social status, "kindness", politeness in your approach, physical attractiveness, etc.
For what it's worth, as a kid, I went through my developmental years highly introverted and quiet. I even have a very specific memory in grade school of having a finger stuck in my face and the insult of "you are the ugliest boy I've ever met" stuck for a looooong time.
I can understand becoming disillusioned with regards to the opposite sex, especially when you're young, impressionable, and easy to anger.
I just don't know how that could ever be an excuse to slaughter innocent people on its own, there seems to be something more psychotic about a dude who cheers violence against people and becomes part of this "incel" thing.
