Wow, that was bad. Yes you were right to be upset.
Be proactive in future, a little assertiveness has never hurt anybody.
If such a situation arises again, ask for the process to be changed.....to say, write about the two people to your left.
Sometime the leaders of the group therapy is inexperiences or just tired and has a slip up.....lets gently help them out.
I think that way you most certainly will go away not feeling so bad and you might certainly avoid others feeling the same way.
Sorry for your bad experience. Chin up.