I completely agree with you. Dignity and respect is the basis of a strong community. In that sense having good mods is very important. They should help to ensure this (and of course, not make matters worse like in your case). Users should feel responsible as well, to not just downvote, but say something about it. Peer pressure usually is quite a good way to keep certain behaviours in check.

A while ago, I commented on a post with a meme about overweight people, which was disrespectful in my opinion. I said something about the role of eating disorders and societal pressure to lose weight in the development of obesity. So, of course, I was immediately called a fatty, etc by some people and downvoted. However, I was very happy to see that the mods removed these comments and left the ones that were respectful (whether they agreed or disagreed). After a while, I also got upvoted by as many people as had downvoted me. Whether I am being upvoted or downvoted does not matter that much to me personally, but it does say something about the apparent controversity of what I said. I think by good moderation, it was possible to handle this discussion respectfully, even though some people were not able to behave. So, it is a good example, I think.

I think that at Lemmy there are some similar issues with mods and people being disrespectful as we had with Reddit. However, by impression is that it is not as bad as with Reddit, where you seemed to have a lot more negative group behaviour. But maybe I just got lucky up until now. I think at any social platform like this, some people are going to misbehave. Some people just want to take out their agression and it is much easier to do so if you do not have to look the person you are hurting in the eye. So, the response to that is very important, I think.