So you agree that homosexual has scientific evidence related to genes. In fact, the word "norm" is defined as in agreement with human being's expectation. Anything that do not work with human's expectation is called "abnormal". According to science, human beings do not have a brain able to think beyond the 3rd dimension of the world and physicist believes there are 10th dimension out there waiting to be explored, but human does not have that intelligence yet and probably will not if religions still form a large part of human lives.
Almost every ailment that mankind has to put up with has a genetic origin but that does not make them normal. The human species owes its success to the fact that there is a strong sexual attraction between members of the opposite sex.
Those amongst the species that are attracted to the same sex and are unable to contribute to the perpetuation of the species obviously have to be classified as defective.