Yuya, this is an insightful question that seems to trap most inexperienced therapists.
I welcome such communications. It often reveals a benchmark of change when a patient can challenge me. This challenge is exquisitely dangerous to the patient as s/he thinks I will become angry, withdrawn, maybe rejecting, haughty or even narcissistically demand that they the retract their objections if they wish to continue working with me.
These are usually transference based expectations. However, many patients run into inexperienced or un-analyzed therapists who’ve yet to resolve their issues in this fragile domain.
When criticized by the patient, the rule is thus for the therapist: do not attack, do not withdraw from the patient; the therapist accepts the patient’s point of view and then searches for the truth of it.
Once the therapist can acknowledge the delicate parts of the patient’s experience as real and crucial, then, with great tact and skill, the therapist might inquire into the transference aspects of the communication.
A competent therapist will acknowledge her/his contribution to the interaction. S/he will then be able to assist the patient in looking at the historical antecedents of the criticism, and the patient’s fears of stating her or his truth to the therapist whom they feel, rightfully, injured them.