Well, I honestly can't find the verse that says this, either. I mean, the clearest verse I can find regarding that is the one in Leviticus...

Also note Leviticus. 20:13,

For all intents and purposes, that's the same person, saying the same thing, which, as someone pointed out earlier, was Judaic law, as opposed to Christian law. Supposing that is part of Christian law though, how come Christians aren't out killing bunches of people, which is what God said was required? How many Christians also keep kosher, which is also described in Leviticus? How many Christians also sacrifice animals, another of requirement of God in Leviticus? Leviticus also appears to suggest that giving birth is a sin, since it requires the women to give a "sin offering" after a certain length of time has passed from the birth. Ever shave? Get a tattoo (or even just draw on yourself with a pen)? Those are also against the Law according to Leviticus. That book is chock full of things that the majority of Christians now ignore. How is it that Christians find it okay to pick and choose which of God's laws they keep?

In addition to that, I've read other accounts that suggest that the original Hebrew words used, and the later Greek translations, meant a ritual impurity, rather than a violation of law or sin.

1 Corinthians 6:9-10

Which says nothing specific about homosexuality, and applies equally between homosexuality, andheterosexuality.

Romans 1:26-28

The original words used by Paul in this section were also used to describe himself, due to following Christ, as well as using the words to describe God. From what I understand, he was talking about society as a whole, but, that through Christ, such "societal repugnance" didn't matter.

So basically, it all comes down to whose interpretation of the Bible is "correct", and, since no-one currently has an indisputably direct connection to the red phone sitting on God's desk, no-one can speak with authority as to which is the correct interpretation. One viable interpretation can be no more valid than any other viable interpretation.