The Immorality of God - Slavery in the Old Testament

[Thumpalumpacus]

Finally, God communicates perfectly that which we need to know. However, the fact that He keeps His own counsel does not mean that He is imperfect in any way.

Then clearly he didn't think we needed to know that slavery is bad, and you clearly need to concede the argument, given this admission of yours. That is the only honorable option aside from admitting his imperfection.