Why Is Being Gay Considered “Amoral”? [I Am LGBT Friendly]

I could never grasp why being gay is considered an “amoral” act. Nor why people are homophobic in the first place. If God exists, and if God supposedly considers homosexuality a sin, then why is homosexuality so common not just in human beings but also in other animals? If it’s so allegedly unnatural, then why is it in our nature at all?