To my mind, this is a little like people being depressed about The News. The News tends to be negative stuff and it used to be available for an hour or two on the TV. Now, you can access The News 24/7 via TV, internet, radio, etc.
Some folks find that really depressing because they get so much more negativity in their headspace than they used to. A primary approach to not being depressed about The News is to stop letting it take up so much of your time and attention. Actively seek to tune it out and focus on other things.
Similarly, the internet is bigger than it used to be, so some of this is perceptual and/or a numbers game. It's easy to find fightiness and feel like "It's everywhere." It's relatively easy to take good things for granted and underappreciate them.
Some things I find helpful:
1. Actively seek constructive engagement. For me, this involves declining to indulge the knee-jerk reaction to rebut anything and everything that directly disagrees with some comment I made (ie replies to me that tell me "You are wrong!" or similar). This is a bad habit of mine that just makes things worse and no amount of trying to justify to myself why I tend to do this makes it not a bad habit.
2. If I do choose to reply to people who disagree with me or who are being negative, think about what my goal is and what I'm trying to accomplish. Is there particular information I would like to put out as a result of their comment? Can I do it without just going down that path of "No, you!"?
3. Grow a thicker skin. I don't absolutely have to have every single person who replies to me on the internet like me, be nice to me, be my friend, blah blah blah. It's okay for other people to disagree with me and to talk about what they think. I can decline to take it so freaking personally that the entire world doesn't always agree with me.
4. Keep in mind that people are much more likely to reply to you online if they disagree. There isn't a whole lot to say if you agree and HN in particular actively discourages low value replies. So you aren't going to see a lot of vacuous "Me toos" here. That doesn't mean people here hate me.
5. View some of it through the lens of "HN/The Internet is bigger than it used to be. It's a numbers game. Multiple replies disagreeing with me say more about that fact than about me, this opinion, etc."
6. Work on my communication skills. This is an ongoing effort. Some phrases or framings tend to get knee-jerk negative engagement. Learning to say it better helps reduce the nonsense.
At the same time, I try to make my peace with the fact that no amount of effort on my end will ever completely put a stop to other people choosing to do whatever the heck they choose to do. "You can't please all of the people all the time" and that sort of thing.
(This comment is not intended to be comprehensive. It's just an off-the-cuff forum comment, not a PhD thesis.)