The assertion that opposite-sex attraction is "normal" and that same-sex attraction is abnormal is not supported by science.
I don't know what "science" you are referencing but according to the NY times [0] 0.003% of marriage in the US are homosexual. To put that into context 0.006% of the population has 2 different colored eyes [1]. I would call someone with the same color in both eyes to be more "normal" than someone with different colors.
Now to the point. It may be true that there is no scientifically proven conversion therapy, but that is the case with many psychological characteristics. Many people have mental "things" (I won't call it a mental issue because it is not inherently bad, but you get my point) that science has no proven way to treat. But scientists continue to try to find a treatment. Of course there are limits to what they can try. Shocking genitalia is not allowed for any therapy and as such is not allowed for conversion therapy. But there are many other effective methods that psychologists use to help people who want to change.
[0] https://www.nytimes.com/2016/09/13/upshot/the-most-detailed-... [1] https://www.medicinenet.com/heterochromia_iridis/article.htm...