I disagree also, as i do with those who simply look at the requirements of slave owners, in a society in which this was a intractable cultural institution, which requires a situation to be managed, in contrast to aggressive detrimental attempts at abolishment.
By allowing a greatly ameliorated form of slavery which works towards societal abolishment, which we now take for granted, Christianity as a minority faith can exist in such cultures.
It may shock Marxist theologians and advocates of the social gospel, but while it certain disallows abuse and tyranny, etc., and promotes just the opposite, the N.T. is not foremost concerned with social revolution of the world without, but of believers being spiritually victorious in whatsoever situation they or the church finds itself.
Christianity was not birthed with a silver spoon in its mouth, and its Founder was birthed in a feeding troth, and the apostles were treated as scum of the earth, and yet it grew by purity in power and in population.
2 Co 6:9 As unknown, and yet well known; as dying, and, behold, we live; as chastened, and not killed; As sorrowful, yet alway rejoicing; as poor, yet making many rich; as having nothing, and yet possessing all things.
The Bible has eternity first in view, and then works to effect change on earth. God’s will as done in Heaven’s life sets the example for that on earth, and love for God is what primarily motivates man, over that of men rulers, etc, and there is more than just a requirement to obey one’s master in the verse you quote. Servanthood is esteemed, and while they (we) are to be “doing service, as to the Lord, and not to men,” as God will reward them, so also masters are required to “do the same things unto them, forbearing threatening, knowing that your Master also is in heaven; neither is there respect of persons with Him.” (Eph. 6:8,9).
Add to this that owners must give just and equal recompense (Col. 4:1), and those who withhold pay are condemned in no uncertain terms, (Ja. 5:4-6) and an escaped slave (in Rome that was bad news) was offered back to his owner, but no longer as a slave, but a brother, even as Paul himself, (Philemon) and freedom was to be sought if it could be had, (1Cor. 7:21) together with the 2nd great command, and we have a better idea of what was required of a slave owner. That being that even slaves choose to stay then they would be family if believers, and if not, then woe to them who hindered their conversion. (Mt. 18:7; 2Cor. 6:3)
I would agree with much of what you have said. Particularly with the view that a Christian’s view should be towards heaven and in doing so, give preference to that which will be rewarded in heaven even at the expense of that which is profitable in the world.
However, to say that slavery is evil (sin) is to take a step further than the gospel or NT is willing to go. While quite possible God’s intent ... going beyond God’s stated word, is not a comfortable place for me.
Call slavery unnecessary, call it unwise or foolish, call it ill conceived, call it a path unto temptation even .... but to ADD TO THE BIBLE (Rev 22:18) appears to be a dangerous thing and is not a step that I am willing to take.