Gamers--it's a large group of individuals who associate with a culture that has, for a long time, not been accepted as part of the social norm. It comprises of men and women who tend to score very high in video games but do not perform very well in social situations. Games have taught this culture to get frustrated at, hit, and manipulate the things which are deemed antagonistic, rather than flex a more civil muscle to find a social based solution that is not destructive.
As the use of computers and gadgets has become common place, the moniker of 'gamer' applies to nearly everyone. Suddenly, the same demographic that was always picked last at school gym are now part of the mainstream.
Enter feminists into video gaming. This classification of people are challenging video game narrative much in a same way a community challenges a government. Everyone should have a right to express their perception of a situation which affects them negatively, as a means to change this situation, regardless of the validity of such a claim.
The claim put forth by feminists like Sarkeesian is that, although many women play video games, women in video games are not represented in a manner which fairly and truly caters to female gamers. In other words, women are the last to be picked at video game gym.
My experience as a computer using geek growing up was very much like explained: I was a sort of social outcast at school. But there were always others like me. I recall (what is likely a normal phenomenon) that other social outcasts at school would bind together and socialize. There were the computer nerds, the math nerds, the band nerds, the drama nerds, the D&D nerds, the card playing nerds, and others. They were of varying ages, races, genders, sizes, and so on, but they tended to have one thing in common: they were gamers.
My experience is why GamerGate saddens me: it's a fomerly rag tag group of unique individuals now fighting to exclude outside thought and defend the norm.