Reason and logic. Absolutely homosexuality is a disorder often caused by physical deficiencies (hormones, sexual organs development, mental illness, social enviroment, etc). Just because someone has an urge or a tendency, does not make it sane, natural or logical. The difference in mental fitness is in the fact that homosexuals do not process the value of the intimate union, friendship, growing together with the opposite sex. They lack that natural sense of wanting to unite with the opposite sex. Nature, in it's overwhelming majority, beginning with fully developed human beings, is hetersexual. There is nothing more natural than the union between a man and a woman, highlighted by the union's ability to reproduce without artifical methods.