I don't think it is appropriate for T to display anger AT the client. I think it is appropriate for a T to say for example "I am angry that happened to you" and model feeling anger, but I think therapists need to watch their reactions.

And when it comes to countertransference, T's that get angry because of it need supervision.

While many clients may not have a history of seeing anger displayed correctly, I don't think T's should display it AT the client. Yelling at me/client does nothing but make me want to run away.