This was a thing on reddit too. Don't think that Lemmy is immune to group think or even bots intentionally farming divisiveness. If anything, the inconsistent moderation by design makes it even more susceptible.
I try to tell myself to just roll my eyes at pointlessly negative comments, throw it a downvote if I think it's not contributing anything useful, and move on. Otherwise they'll drag you to their level and beat you with experience, as it were.