Homosexuality is not a sin

By whose definition is homosexuality not a sin? Or by what factor can we make this claim? Society? Consensus? The hive mind? Opinion? The state? The internet? Biology? Psychology?

Who can claim that they are God that they can determine what is sin and what is not sin? Or if they do not claim to be God, how could they declare homosexuality not a sin? Sin is a religious term, not a biological term. Not a psychological term.

@ironshield