The constituents & legislatures wouldn't be happy.
the legislators are the ones writing it ad approving it.
Is it for a politician to decide what's harmful?
its for the evidence to show and there is a mountain of evidence that shows conversion therapy is not just ineffective but actively harmful
Amy Przeworski, Emily Peterson, Alexandra Piedra. A systematic review of the efficacy, harmful effects, and ethical issues related to sexual orientation change efforts. Clinical Psychology: Science and Practice 2020.
Steven Meanley, et al Lifetime Exposure to Conversion Therapy and Psychosocial Health Among Midlife and Older Adult Men Who Have Sex With Men. The Gerontologist 2020
Haldeman, Douglas C. The practice and ethics of sexual orientation conversion therapy. Journal of Consulting and Clinical Psychology, 1994
Christi R. McGeorge, Thomas Stone Carlson, Russell B. Toomey. An Exploration of Family Therapists' Beliefs about the Ethics of Conversion Therapy: The Influence of Negative Beliefs and Clinical Competence With Lesbian, Gay, and Bisexual Clients. Journal of Marital and Family Therapy 2015
Robert J. Cramer,Frank D. Golom,Charles T. LoPresto &Shalene M. Kirkley Weighing the Implications of Conversion Therapy Evidence: Empirical Assessment and Ethical journal of Ethics and Behavior Mar 2008
Douglas C. Haldeman Therapeutic Antidotes: Helping Gay and Bisexual Men Recover from Conversion Therapies J of Psychotherapy 2008
Alex R. Dopp. Treatment of Sexual Minority Youth: Ethical Considerations for Professionals in Psychology. Ethics & Behavior 2013
Madison Higbee, Eric R. Wright, Ryan M. Roemerman. Conversion Therapy in the Southern United States: Prevalence and Experiences of the Survivors. Journal of Homosexuality 2020
Jaco Van Zyl, Kathryn Nel, Saraswathie Govender. Reparative sexual orientation therapy effects on gay sexual identities. Journal of Psychology 2017
Julianne M. Serovich, Shonda M. Craft, Paula Toviessi, Rashmi Gangamma, Tiffany McDowell, Erika L. Grafsky. (2008) A Systematic Review of the Research Base on Sexual Reorientation Therapies. Journal of Marital and Family Therapy
Julianne M. Serovich, Shonda M. Craft, Paula Toviessi, Rashmi Gangamma, Tiffany McDowell, Erika L. Grafsky. A Systematic Review of the Research Base on Sexual Reorientation Therapies. Journal of Marital and Family Therapy 2008
and literally thousands more
see above