I agree wholeheartedly.
Even though you already agreed to see the child's therapist, I think you should not go. This is your ex's hired gun. Submit a response that says you just learned of this code and feel it would be better to find a neutral evaluator. You can even say that you do not believe, based on previous statements made by this therapist and the willingness of this person to violate code and act as both therapist and evaluator, that an unbiased evaluation is possible from this therapist.
Request a separate, impartial evaluator, preferably one that you know to be familiar with parental alienation tactics. Consider a new attorney, also.
Psychologists and counselors often get "recruited" by alienating parents who want to legitimize their desires to cut off the other parent. Many counselors fall into this trap without realizing it, especially those who have their own bias that favors the parent recruiting them.