The sin that resulted in the destruction of Sodom & Gomorrah has traditionally been viewed to be homosexuality (hence the term sodomy).
But many pro-gay theology apologists now try to say that it was due to inhospitality or other reasons, but definitely not homosexual behavior. They point to some verses that appear to support their view but ignore many others.
Check out this excellent piece for a thorough analysis supporting the traditional view — Stand to Reason: What was the Sin of Sodom and Gomorrah?
Piecing together the biblical evidence gives us a picture of Sodom’s offense. The sin of Sodom and Gomorrah was some kind of activity—a grave, ongoing, lawless, sensuous activity—that Lot saw and heard and that tormented him as he witnessed it day after day. It was an activity in which the inhabitants indulged the flesh in corrupt desires by going after strange flesh, ultimately bringing upon them the most extensive judgment anywhere in the Bible outside of the book of Revelation.
Here’s an example of the flawed theologically liberal reasoning. Some claim that the punishment was because the men of Sodom tried to rape the angels in attendance, but that doesn’t make sense.
Was the city destroyed because the men of Sodom tried to rape the angels? The answer is obviously no. God’s judgment could not have been for the rapacious attempt itself because His decision to destroy the cities was made days before the encounter (see Genesis 18:20). Further, Peter makes it clear that the wicked activity was ongoing (“day after day”), not a one-time incident. The outcry had already been going up to God for some time.
The inhospitality claim also falls flat.
. . . are we to believe that God annihilated two whole cities because they had bad manners, even granting that such manners were much more important then than now? There’s no textual evidence that inhospitality was a capital crime. However, homosexuality was punishable by death in Israel (Leviticus 18:22, 20:13). Does God ignore the capital crime, yet level two entire cities for a wrong that is not listed anywhere as a serious offense?
Read the whole article and bookmark it for the inevitable objections you’ll get from theological liberals. It is a great example of how to properly analyze biblical texts, and especially so for controversial or difficult passages.
Also see Responding to Pro-Gay Theology, which addresses the most common biblical fallacies of the movement.