I took over a sub that was frankly super toxic. Over the years, I realised that for a community to have healthy conversations you have to enforce it, and you have to model good discussions. It's hard work.
I've actually done most of what Anil recommends in this post. Most excellent read.
"Fix your communities. Stop allowing and excusing destructive and pointless conversations to be the fuel for your business. "
https://www.anildash.com/2011/07/20/if-your-websites-full-of-assholes-its-your-fault-2/