That's a very vague comment to make without naming the subreddit and the topics being discussed on it. What are the "controversial topics" and what are the "truly dangerous ideas"?
Sorry for keeping it vague. The communities loves to write endless heapings of words, so I’m sure if and when it is banned, much ink will be spilled. Perhaps another member of the community will recognize which it is I am talking about (there is overlap with the HN crowd) and be able to summarize better than I.