I think you're referring to https://news.ycombinator.com/item?id=14692957.

This was a tough one. I ultimately decided not to vouch it, and I'd like to try to explain why. It doesn't have anything to do with the content or my own feelings on the matter, but rather the way in which the idea was presented.

I agree that it was in good faith, and it was also substantive. But it's not really neutral:

"But seriously? Do I live in an alternate reality where drunk people do all sorts of borderline illegal inappropriate stuff on a regular basis?"

"It may seem insensitive, but I am being pragmatic: whether or not something "haunts" you has as much to do with your way of framing an event and your attitude towards trauma as the actual event.
Just because someone else did something wrong is no reason to carry it with you for years."

I can only describe my own perspective on the comment, which may not represent everyone else's. But the reason that I feel the flag is deserved is that even though the comment is written in good faith, it presents your side as clearly correct. The implication is that if anyone disagrees with you, they must be mistaken.

The phrasing "Do I live in an alternate reality...?" sets up the reader to want to disagree with you. It's argumentative rather than pensive. It's entirely possible that your life experiences are an outlier rather than representative. E.g. I agree that drunk people tend to do risky things, but in my own life, my friends manage to restrain themselves pretty well. I'm probably the outlier rather than you, but the point is that framing the argument as can't-possibly-be-wrong is poisonous to thoughtful conversation.

That leads to the other issue, which is that it blames the victim of harassment for feeling harassed. It's certainly possible that whether you're harmed by an incident is a matter of perspective, but it's not automatically up to the victim to fortify themselves. If someone is legitimately distraught over an incident, they'll carry that with them in ways that alter their future behavior to their own detriment. The core difference is the betrayal of someone you trusted and respected: if you're harassed by someone on the street, you can shrug it off. If someone you respect tries to force you into a corner and plant their lips on you, you're going to freak out and wonder how many other people in power are secretly this way, and how you could possibly be so naive to think they weren't. That sort of betrayal can stay with you for years.

So it's not that your comment was mistaken, but rather the nature of your phrasing tends to exclude thoughtful replies from forming, combined with the fact that the topic itself is extremely controversial. It's very difficult to react well to someone who both blames the victim and sets up an argument as if their life experiences are representative of the norm. (But I totally agree with you that it was written in good faith! I was just trying to explain some of the reasons why it got flagged, not call you out on anything.)

One thing that helped me in this regard was to phrase my controversial ideas as questions. "Drunk people tend to do reckless things. Would it be a good idea to cut him some slack in this case?" is far more likely to generate thoughtful comments than "Drunk people do reckless things. I can't believe that we're not cutting him some slack."

Hope this helps clarify a bit. The overall point is that if you put a lot of conversational passion into your side of the argument, this typically causes the other side to give an equally passionate rebuttal. But that's just another name for a flamewar. That's why it's better to be dispassionate yet substantive.