A PMHNP is facilitating a process-oriented therapy group for adults with depression and anxiety that has been meeting weekly for six weeks. During this session, two members openly disagree about whether personal disclosure should be expected of all members, one member directly challenges the therapist's authority by stating 'You don't really help us, you just sit there,' and another member threatens to leave the group. Previously cohesive members are taking sides, and there is palpable tension in the room. Which stage of group development does this behavior most clearly represent, and what is the therapist's most appropriate response?