First, do no harm. That has long struck me as the medical practitioners' version of the Golden Rule common to all of the world's great religious traditions. In my faith, we follow the Rabi Jesus, who said "do unto others as you would have others do unto you." 

In practice that looks like, first, doing no harm. It also looks like acceptance of each child created in the Divine image. It looks like respect for each child as created. It looks like love.

Conversion therapy looks like none of that. It does demonstrable, measurable harm. It shows no respect or acceptance, and it is not loving. It should be banned.