I think it's important to realize as well that the majority of 18-25 year olds are heavy, daily users of the internet, and this facade of the internet in particular. Even if the users who are over that age use it as heavily, they are probably in the minority of their age-group. This means that the 18-25 year old assholes are more in force than the older assholes. None of this is something I've researched, and you should take it with at least a grain of salt considering I haven't posted a source or done more than spitball. But I think this is also because there is a volunteer bias happening here. Because while a lot of my older technophile friends are on Reddit, a lot of the racist/sexist/bigots are not. So. I don't know, that's some anecdotal evidence for you.