Unfortunately I think this just reflects human nature. The more people you have the more people you have at the fringes who are aggressive, or trolling or even just selfish or insensitive.
Also it's easy to come across rude when posting in text - anyone who works with colleagues via email will find the same problem of one meaning being intended but a different meanong (such as tone) being read by the recipient.
When you have a small community your names become familiar and there is something personal about the interactions. Once the you have a huge community people become anonymous and that allows bad behaviour to flourish. I barely ever saw a name twice on reddit and that's happening here too. I got to the point on reddit where I'd post a comment but I wouldn't ever read the replies as I was fed up with dealing with the negativity.
My hope for the fediverse is that there will be multiple versions of the same communities so that we can have closer knit versions of communities as alternatives to the 1m+ chaotic versions. Small communities are where you can achieve decency and kindness more consistently.