And it bears remembering that the debate happened in the first place because Brown went on a chest-thumping tirade of bravado about Savage's remarks regarding the Bible: "Let me lay down a public challenge to Dan Savage right here and now. You want to savage the Bible? ... I’m here—you name the time and place and let’s see what a big man you are with someone who can talk back."
Savage's point about slavery and the Bible is a sound one that I've made here before. Several times. He notes, rightly, that "the Bible got the easiest moral question that humanity has ever faced wrong, and that was slavery. And my ... point was that the Bible, if it got something as easy and obvious as slavery wrong, what are the odds that the Bible got something as complicated as human sexuality wrong?"
Brown shoots back that slavery in ancient Israel was much better and more progressive than the slavery practiced by its neighbors. As far as I understand it (I am not a student nor a scholar of the Hebrew Bible), this is correct. But he went on to say, "But if you move to the New Testament, this is much more like indentured servitude. People would sell themselves essentially into a period of indentured servitude, usually between six and seven years, and then they could be released, and they could get money for that. Now this wasn’t always the case; this is very complicated."
The only part of that quote that is actually accurate is the last sentence. It is a routine lie of Christian apologetics that slavery in the Roman imperial period (in the first and second centuries CE, when the New Testament was being written) was largely indentured servitude of a temporary nature. This is a flat-out lie. No scholar of antiquity that I am aware of would make such a claim, because all of our evidence says otherwise.
To simply quote from the Oxford Classical Dictionary, "Slaves were produced chiefly as captives in war." While debt-slavery is indeed attested in parts of Greece at an earlier period, it was dwarfed by the number of non-Greek, "barbarian" slaves brought into Greece or the number of Greek slaves made by prisoners of war.
But in the Roman period, that is, in the period when the New Testament was actually written, slavery was largely the product of war. Captives were made slaves, and when they reproduced, those slaves belonged to the master. While it's true that slaves were freed in large numbers and could even go on to vote and have successful careers, that doesn't mean the institution itself was any less brutal or wrong, or that it was merely a temporary station used to make money. It wasn't. The slave did not have authority over his own person (sui iuris), nor was there any assurance that he would ever be freed. He was the property of his master, who could quite literally do anything he wanted to his slaves.
So when the New Testament, repeatedly, enjoins slaves to obey their masters (1 Pet. 2:18, Titus 2:9, 1 Tim. 6:1, Col. 3:22, Eph. 6.5), it is sanctioning this institution by asserting its chief component: obedience. What's more, several authors likewise throw in other less-savory aspects of slavery that were nonetheless endemic to it, namely fear ("with fear and trembling": Eph. 6:5; "fearing the Lord": Col. 3:22), and even violence, as in 1 Peter 2:19-25, a truly horrifying passage wherein slaves are told to obey their masters even if the masters are "harsh" and even if they beat their slaves.
Brown goes on, like most apologists when speaking of slavery, to suggest that Paul, in the book of Philemon, "tells Philemon to take Onesimus [his slave] back, not as a slave, but as a brother, a dear brother in Christ." While Paul does say that, he uses no language of manumission, and he nowhere instructs Philemon outright to free the slave, nor does he ever question the institution of slavery, even with an obvious example of its injustice prompting the letter to begin with: for Onesimus had apparently run away, and Paul, in accordance with the law, was sending Onesimus back -- pleading on his behalf for mercy, but sending him back nonetheless. When Paul was faced with his own type of Dred Scott decision, he failed to make the moral choice. He sent the slave back.
Christian apologists desperately want the New Testament to be univocally against slavery so that they can continue to assert that other prescripts also reflecting ancient ideologies be followed today (like those on sexuality and gender hierarchies), but it simply isn't. While there are some admirable passages about slavery in the New Testament (like Galatians 3:28), the bulk of them not only sanction the institution of slavery, but even the components that allow it to continue, namely the obedience inspired by fear of violence.
Brian Brown may not know that his initial remarks on slavery are falsehoods, but his throwaway comment that "it's complicated" indicates that he does. Nevertheless, the issue of slavery in antiquity is not nearly as complicated as those of sexuality and human relationships, about which Brown and his organization remain stubbornly and rigidly antiquarian.