Absolutely right. It is a transparent attempt to link the image of something abominable -- slavery -- with something perfectly normal -- opposition to homosexuality. If the average pro-hetero can be turned into Simon Legree, it makes every queer a sympathetic soul.
I don't know that God had much to say about slavery, but He makes it pretty clear where He stands on homosexuality.
Actually, the God of the Bible had a lot to say:
Genesis 20:17
Then Abraham prayed to God, and God healed Abimelech, his wife and his slave girls so they could have children again
Exodus 12:44
Any slave you have bought may eat of it after you have circumcised him (ouch!)
Exodus 21:21
but he is not to be punished if the slave gets up after a day or two, since the slave is his property.
Jeremiah 34:9
Everyone was to free his Hebrew slaves, both male and female; no one was to hold a fellow Jew in bondage.
Well, at least then there was some progress for the Israelites at that point in time. Ok, that's soooo Old Testament, how about some New Testament:
John 8:35
Now a slave has no permanent place in the family, but a son belongs to it forever.
Galatians 4:22
For it is written that Abraham had two sons, one by the slave woman and the other by the free woman.
Galatians 4:23
His son by the slave woman was born in the ordinary way; but his son by the free woman was born as the result of a promise.
Ephesians 6:5
Slaves, obey your earthly masters with respect and fear, and with sincerity of heart, just as you would obey Christ.
Colossians 3:22
Slaves, obey your earthly masters in everything; and do it, not only when their eye is on you and to win their favor, but with sincerity of heart and reverence for the Lord.
1 Timothy 6:1
All who are under the yoke of slavery should consider their masters worthy of full respect, so that God's name and our teaching may not be slandered.
1 Peter 2:18
Slaves, submit yourselves to your masters with all respect, not only to those who are good and considerate, but also to those who are harsh.
Certainly, the slave holders of the Old South must have found comfort in those four verses.
It seems that the people who spoke for the God of the Bible were not altogether unhappy with the concept of slavery, unless it applied to them.
You can see why some folks question what they had to say on homosexuality, too. But, then, they are berift of proper interpretation of the writings. Maybe its because they have too much trouble deciding which of the ten thousand denominations of Christianity are the "correct" one.