I don’t like it at all.
My two cents: Sometimes we need to be angry. Sometimes our anger prevents us from staying in an unhealthy situation.
Sometimes, no. Sometimes anger serves no purpose except to make us kind of grouchy.
But I have faith that you'll work through the anger and get to the other side.
A tangent here: My mom died when she was 40, and I was 14. Prior to that, I'd been a deeply religious young girl. I'd prayed for a miracle. I prayed that God would save her. When He didn't, I got angry. I got angry, and I stayed angry for a good 16 years. Until my daughter was born.
I learned something important from that. First, I learned that I probably had needed grief counseling, but since I cannot run my life in rewind, I had to let that one go. Next, I learned that anger is, as you've mentioned, a stage in grief. My problem is I had no outlet; my anger turned inward, and it poisoned me. It turned to hate and pessimism, and that's not who I am.
I got into therapy and really worked on that anger, learned that my anger helped me feel less vulnerable. As a 14-year-old girl, staying angry made sense. Better not to be vulnerable; people can (and do) prey on adolescents. But the anger didn't make sense when I was in my 30s.
For me, on the other side of anger was acceptance. Along with acceptance was peace and the recognition of just what I could control. And I couldn't control my mom getting sick and dying.
Learning that has helped in working through my STBX leaving. I still get angry, but I don't stay angry, and I'm actually pretty sure when I'm on the other side of this divorce that I'll find acceptance for what my STBX and FIL have done, and I'll again have a bit of peace.
TMD