A private chat thread released this weekend reveals that banning hate speech on Reddit is apparently too difficult a job to even attempt.

The news, first spotted by the Huffington Post, comes from a leaked conversation between Reddit CEO Steve Huffman and Reddit user Zachary Swanson, known as “whatllmyusernamebe” on the site. Swanson asked Huffman to reconsider his permissive stance on hate speech on the site, pointing out that Reddit’s rules already ban “violent” speech, which the site defines as “content that encourages, glorifies, incites, or calls for violence or physical harm against an individual or a group of people.”

“There’s a reason why it’s not really done.”

In response, Huffman argued that hate speech is “difficult to define,” adding that enforcing a total ban on hate speech is “a nearly impossible precedent to uphold,” and “impossible to enforce consistently.” After speaking with Huffman, Swanson posted screenshots of his conversation in a pair of subreddits, including r/stopadvertising, which is dedicated to curbing hate speech on the site. After he did, Swanson received an email saying he was suspended from the site for a week on charges of harassment.

This isn’t the first time Huffman has found himself in hot water over his stance on hate speech. Back in April, Huffman found himself embroiled in controversy for refusing to moderate any of the blatant racism happening on his site. At the time, he said that Reddit’s stance on speech is to “separate behavior from beliefs,” and that hate speech did not constitute a “behavior”. Users were specifically asking Huffman about this in relation to r/The_Donald, the subreddit dedicated to the US president that has often come under fire for housing racist or bigoted discussions.

Huffman later clarified that he felt racism was not “welcome” on Reddit, but that he believed “the best defense against racism and other repugnant views both on Reddit and in the world, is instead of trying to control what people can and cannot say through rules, is to repudiate these views in a free conversation.”

Hate speech is tricky to catch without human eyes

As the Huffington Post points out, there are social media sites that attempt to moderate for hate speech, including Facebook, Instagram, and Twitter. The issue is that these efforts typically take human effort. Right now, Facebook works with scores of people — mostly contractors overseas — to oversee content, review flagged material, and decide when something has violated its rules. They’re the ones that inspect user posts to decide what does and doesn’t constitute hate speech. It’s an expensive problem to have, and exactly why the company is currently buying and developing software that specializes in natural language processing to handle this problem with artificial intelligence. Ultimately, the goal is to have an AI that can understand language and intent, which are both crucial to deciding how hateful or benign a certain post might be.

Reddit might not have these algorithms, but the company has decided to police hate speech in the past once it crosses a nebulous line and typically involves a fair amount of public pressure. After months of criticism in 2015, the site shut down a handful of overtly racist subreddit communities, with Huffman claiming that they “violate the spirit of the policy by making Reddit worse for everyone else.” Two months earlier, Huffman had shut down popular homophobic, transphobic, and fat shaming subreddits on similar grounds.