It's because there are assholes everywhere. They are small in number, but they are pretty evenly spread throughout the population. Regardless of ethnicity, socio-economic status, age or any other demographic detail, they are everywhere.
And they always have been, and likely always will be.
I suppose that social media dynamic allows them to disproportionately visit their douchebaggery on the rest of us, but that's not "Eternal September." That's just humanity.