I think there is a very important distinction that needs to be made. The popular reddit experience is vastly worse than the customized reddit. It took me a while to realize that my reddit experience was vastly improved once I was very picky about which subreddits I follow.
True, but The_Donald is always leaking. I've seen plenty of sexist/racist content on subreddits for cities, sports teams, memes, etc. Reddit has allowed itself to be a platform used in part for really despicable content, and the despicable people who generate that content regularly venture outside their cesspools.
Once the site grows beyond those 1st, 2nd and 3rd degree connections, you get exposed to those 4th, 5th and 6th degree connections that might have some values and opinions that are shocking to you because they don't run in your orbit.
I feel bad that the author contributes his time to making a world a worse place. I see Reddit as giving more visibility to the world. It's true there's some crazy stuff from some loud people, but my guess is if it was quantified it would still be a small percentage of actual content on Reddit. But just like in life, a rare shocking event dominates our consciousness much more than persistent normal events.