The kid who did that shooting was a prom king who was facing rejection from a girl he wanted to go out with but who didn't want to go out with him. But, sure, twisted masculine expectations definitely had nothing to do with this and Anita Sarkeesian is a horrible person who is just using this as fodder in her crusade to destroy all men because she thinks they are rapists.
Evil assholes who don't care about the rights of others are impossible, obviously.
Where do you think those come from in the first place?
This kid wasn't borne out of some vacuum, he was raised in and around the beliefs and expectations of his parents, his peers, the media, and society. Now, none of these things together or separately "forced" him into this act, but maybe, just maybe, they had an influence on the person he was at the moment he pulled the trigger, and maybe, just maybe, focusing on at least one of these particular factors might stop someone else from falling down that same hole one day in the future.