Reddit is a collection of communities. I like several of them, and think they are generally good and uplifting, /r/pixelart for instance. Some communities have some pretty bad people in them, but it is impossible to create a social media site at scale without like-minded bad users creating and/or flocking to bad communities.

People are in different stages of life and seek solace in other people having similar experiences. Thus, the sexually frustrated congregate, the depressed congregate, drug enthusiasts (and abusers) congregate, disgruntled ex-<insert organization> congregate, you name it, and angry/sad/anxious people with a shared condition will congregate in search of validation/confidence.

But the opposite is also true - people with a shared hobby/passion/vision congregate as well and create some really fun and uplifting communities.