Conversion therapy treats queerness as something inherently wrong and to be fixed. Therapy for mental illness is sought by individuals who find their quality of life suffering due to said mental illness. Queerness does not affect the quality of life - it is simply a facet of a person. Seeking therapy to remove or improve that facet is of course allowed, but should only be sought by choice and not enforced on a child who cannot speak for themselves in a court of law. Conversion therapy should only be allowed for those who are over 18.