To stretch it a bit, I'd say there's an important difference between a fire door and reddit. The fire door knows its job is to prevent people burning to death. Reddit... does it know it's job is to prevent outraged reaction?
I think this is one of the things that made facebook so problematic on politics, it can't tell the the good likes, comments and shares from the bad ones. I'm not sure they really had a concept of better and worse. Some stuff isn't allowed, but otherwise?
Imagine one post, where Mrs X invites neighbors to meet a local candidate at her house for revolutionary thoughts and biscuits. Another post, where Ms Y rants about Macron voters, Trump, taxes and kids these days. Both are political. One is actually democratic and participatory. The other is cheap, nasty, unproductive and divisive. Does Facebook, in any meaningful sense, value one over the other? Does reddit?
Reddit has its non-censorship values. I respect that. It's important that someone does. I also think they want to house the weird, and I respect that too. But, I think unrestricted speech may be an insufficient value, like nondiscrimination or atheism. It's not enough to build on. You need positive values too.
Free speech is also problematic, when taken as 'all speech is equal.'