A flaw of communities is the more emotional the post, the more persuasive it seems.
Angrier posts are more likely to be accepted as true by new members and attract more likes/comments (thus appearing at the top of the community for all members).
It doesn’t take long for members to realise that the angrier they post, the more attention they get.
If you let angry posts stand, your community soon becomes filled with them.
Two approaches can help here. The first is to have a rule or create a norm, against posting angry (frame it as posting unprofessionally).
If the post is clearly provocative or incites further anger, you need to address the issue directly with the member and remove the post. Members can be critical as much as they like, but they can’t use flagrantly angry words to incite anger from others.
The second is to copy Denise’s approach and have a group of members who step in with a friendly tone and prevent issues from escalating.