There is absolutely no credible scientific organization that supports the concept of conversion therapy for members of the LGBT community.  They are all against it.   Allowing conversion therapy because a therapist wants to practice outside of the guidelines of any professional organization would be the same thing as allowing an oncologist to treat a cancer patient with laetrile.   It is harmful and unsupported by any scientific studies.  Follow the science.  Follow the research.  There is scientific basis for conversion therapy.  If there were, let the supporters submit to it, and be converted to become gay.  They know that it doesn't work, but support it because of their own biases and bigotry.   It must be banned.  Any other decision would be counter to the available scientific evidence that you must rely on.  You must ban this barbaric practice.