I see your points, and I agree that trying to work through anger, let go of it, move beyond it, etc is a worthy goal. However it’s been my experience that anger is a natural and uncontrollable “reptile brain” reaction to certain circumstances.
What we DO with anger is our choice. We can choose how we express it, whether we hold onto it or let it pass, etc. But just labeling anger as “bad” sometimes encourages people to try to shove it down, deny it, project it onto others, etc. which I believe can actually have worse effects that if the anger is allowed to be experienced or addressed in whatever way is appropriate to the situation.