I spent a lot of time in my teenage years on IRC, talking about technology until late hours, so this resonates :).
I think I see what you're getting at, so let me reassure you a bit, and correct for any miscommunication I may have caused:
> But forbiding topics is throwing out the baby with the bathwater. It's admitting defeat.
HN doesn't strictly forbid controversial topics. The guidelines[0] outline what is and isn't considered on-topic, provide heuristics for good behavior and pleas to avoid certain bad patterns. They don't say, "these topics will be automatically removed", or "these topics will get you insta-banned". They're just guidelines, a description of what this place should strive for. They work as a Schelling point[1] for individual participants.
So what happens in practice is, when you post a clear-cut intellectually stimulating hacker topic, it'll get upvoted. If it's boring, it'll get ignored. If you post a completely garbage submission, it'll get flagged faster than you can refresh the site. If a topic is on a fence, the balance of upvotes, flags and vouches will lean one way or the other. It's an organic system, but the direction it's leaning is strongly shaped by the guidelines - the one thing everyone knows everyone is expected to know :).
It's also easy to observe that whether or not a given topic stays on the front page or gets quickly flagged out of it isn't just a function of the topic and the source - but also the context (and I think sometimes the timezone). For example, political news aren't very prominent on HN, except when something really big happens, and HN briefly turns into a 24h news station.
And on the controversy itself, the general principle is - it's not the topic being controversial itself that's the problem. The problem is if the discussion around it decays into low-quality bickering. For some topics this is almost a law of nature, so people flag them on sight. But others only get flagged down if and when they evolve into actual flame war.
All in all, I think it's a decent system.
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[0] - https://news.ycombinator.com/newsguidelines.html
[1] - https://en.wikipedia.org/wiki/Focal_point_(game_theory)