The old reddit, allowed actual pedophiles to describe their issues in ask reddit threads.
Theres even a dark ama where a relation which would make people ill, was discussed.
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Unfortunately what social media is exposing, is weaknesses in how human beings agglomerate.
If someone makes a forum for dead baby jokes - distasteful to many, but not harmful in private - it eventually attracts people who think that dead baby jokes are the norm.
Or in worse terms - a sub for making offcolor jokes soon gets overrun by people who think off color jokes are not a risque deviation from normal behavior, but is actually normal behavior.
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On top of this, the internet and social communities are extremely low on contextual information - which is critical for most people to understand a conversation in real life.
This means that the only way someone can know what you mean when you are being vague, is if you make an constant effort for tonal and idea accuracy in your comments.
Obviously this is challenging, leading to a cascade of misunderstandings, which only serve to polarize groups more.
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Theres a lot of research being done on how people behave online, and its just a grim picture.
How Community Feedback Shapes User Behavior (https://arxiv.org/abs/1405.1429)
The spreading of misinformation online( http://www.pnas.org/content/113/3/554.full)
The effect of the ban on hate subs on reddit (http://comp.social.gatech.edu/papers/cscw18-chand-hate.pdf)
The other wave is the circle-jerk - a relentless and all-encompassing embrace of confirmation bias, institutionalized to keep a fundamentalist purity of thought. This is beyond a normal echo chamber, these are high powered ideology amplifiers.
We've never had the concept of unlimited freedom of speech, and most of the time that its been curtailed, it has been to protect against those who use it in bad faith (fire in a crowded theater, etc). That is the toxicity - IMO Reddit is going to learn this lesson far too late, and allow a group that doesn't want to be there anyway take down the whole site when they leave.
When you change your searching and indexing algorithms to suppress fans of a specific politician but not fans of other politicians, that's not really good faith.
In an age where any opposing opinions are consider "toxic" by some, I don't think trying to "detoxify" should be a goal. If you don't like the opinions of a subreddit, don't go to that one.