That one and some others were deleted by order of then-CEO Ellen Pao, it was like throwing a lit match into a powderkeg. The things r*ddit holds most dearly - misogyny, racism, and xenophobia - erupted from its sizeable population of reactionary neckbeards into a shitstorm of fist-pounding tantrums like nothing the site had seen to that point. The insults and threats of violent fantasies were endless and many were Sinophobic in nature. A few years after it happened I remember a discussion (maybe on /r/ShitRedditSays or similar) around how the bigots who inhabited /r/FatPeopleHate et. al., were heavily overlapped with same crowd who would later be found in The_Donald and related right-wing hate subs.

NATOpedia has an article for her and there's some detail on this incident if you want more slop on it (I didn't read every word of the article, just skimmed, so can't say whether it's tainted/biased by one of the neckbeard power editors).

Oh god I used to be subscribed to that subreddit.

The reaction to the removal of an obvious hate sub was what made me re-evaluate my outlook on life. I remember everyone going "we weren't ACTUALLY hating fat people. We were saving their lives by bullying them thin"
and I thought "wait, but I thought we did hate fat people That's all that was ever posted, I thought we all just agreed that it was fun and good to hate them. Why are you lying?"

Then seeing all the responses rightly pointing out how fucked up an outlook you'd need to have to hate people for being fat made me reconsider not being a dumb asshole.

Now I'm perfect of course ✨✨

God the one good thing did was to glass those disgusting subreddits and of course the abhorrent people reacted that way against the removal.