Censored environments like Reddit don't have the least hate because they aren't encouraging it, but because they are incapable of being used for communication between parts of humanity that exist, and will continue to exist for the time being. They are as a sandbox/playpen is to a real social environment - somewhere for children to learn and play around, but not much more. The bigger questions, disagreements and problems we face as a world are going to involve hatred and conflict before they are resolved.
Also, the answer isn't to suppress speech so it goes and hides under the surface, it doesn't go away and the people exposed to it never hear the counter points. The communities you talk about, like reddit, hate speech gets downvoted, it gets counter argued. Bring dumb hateful ignorant views into the light, so they can be addressed, if not for the purpose of convincing the OP (which is often futile), convincing anyone who might be on the fence or sympathetic at least partially to some of their points can understand why its wrong. The problem is when boards or sub-reddits become insular so never face opposing views, on either side, going back into bubbles or group think does not lead to moderate opinions and compromises, just like proving someone wrong can sometimes just cause them to double down on their opinion.
All of these sites are extremely heavily moderated, which is understandable, but saying that they are "anything goes" is false by any stretch of the imagination. Honestly before last year, Discord was the place to be, no matter what your topic was. One of my favorite places to hang out was a place called "Meth and Funamines," which doesn't sound pleasant at the surface, as it's a bunch of druggies. The major rule was "No sourcing," but nobody went there for sourcing, and rarely to discuss drugs. When people did discuss drugs, it was similar to /r/drugnerds. It was just a community of mostly chill people, posting art, poetry, supporting one another be it mental illness or otherwise. No matter who you were, you could come to that server and find a friend in a time of need.
It was wrapped up in the ban of alt-right and other 'hate' discords early this year. Other than discussing drugs, I never saw a single bad thing come from that discord.
These days, I don't know where anyone can go to be free. Self-hosted options obviously, but that is not the answer. Self-hosted services don't have the accessibility or open-ness that sites like Reddit and services like Discord provide.
I wish Discord would provide self-hosted servers and just handled keeping them on a server list. It just sucks.
Which doesn't make the concept any more valid than if the opposite were true.