It is not a matter of having it "both ways". It is a matter of understanding society and God's role in the midst of society. I noted that at the time of Exodus, slavery was a fact of life on this planet. No one knows exactly how it started, but it seems clear judging from later customs that it may have begun either as payment (one person owed another, and they worked it off--not having money in those days. The other possibility is that war played a part: Either kill the enemy, or to be more humane, make them servants (slaves). I also noted that under God's Law, by the time of the current era most Jews eschewed slavery altogether.
That statement would indicate that God just "Showed up" at some point, rather than having created man and been with him from the very beginning. If anything, we KNOW the bibilical origin of slavery, in Genesis 9, when Ham sees Noah naked after the guy got falling down drunk, and Noah cursed Ham's children with servitude. (Later on, people would insist that Ham was the ancestors of Africans, therefore slavery of black people was okay. the Mormons would take it further and say Ham was cursed with dark skin, because they were obsessed with that kind of thing.)
Now, you seem to want God to have gotten on His loudspeaker and announced to the planet slavery is wrong. Yet, you (an example of a human being) already know it is wrong. We also know that their is human trafficking (slavery) still being done today, even though those people also know it is wrong, even if you were to televise to them it is wrong. You seem to think you, today, are the only person over time to realize that whatever slavery once was, what it became, whenever that was, is wrong. So wrong, that in the end people were willing to die to end it (and to preserve the Union).
You want things to work in an instant. Slavery is abolished/ended in an instant; people who are sick are cured in an instant; people have all they need in an instant. God reveals Himself in an instant.
First, human trafficking isn't the same as chattel slavery. It's not endorsed by the state. Second, um, yeah, if you have an all-powerful sky pixie who can command stuff, that should have been higher on his "To Do" list than "Don't eat pork" and "Make sure your robes have a blue trim", which were things God took time out of his busy schedule of running a universe to tell the Hebrews to do.
Since you brought up homosexuality. Most of the last part of Genesis deals with sexuality. How things turn out when one is not true to one's spouse; what happens when homosexuality becomes prevalent; etc. The lessons that are being conveyed is when society, as a whole, begins a wide acceptance of loose sexual mores and morals, look for that society to begin its decline. It is simply a Biblical observation, that to succeed a society needs to remain disciplined.
Um, yeah, here's the thing. This is one of those wonderful things that really doesn't match up with History. Rome didn't fall because everyone was having orgies. Rome fell because Empires fall. It's last couple of centuries, it was a Christian Empire, and it still declined despite "morals".
Our own society did not become undisciplined in sexual matters when homosexuality became an issue. We became undisciplined in sexual matters with divorce and openly living together prior to marriage. Why wouldn't homosexuals want this same 'freedom'?
You mean the freedom of actually not having one spouse be property?
Where it may be more rightly said that some Christians want it both ways is if that Christian community approves of divorce and living together before marriage, but then does not want the same 'openness' in sexuality to extend beyond heterosexual unions. Doesn't work that way. Discipline for all, or discipline for none is how it generally works.
Oh, I agree, this is another case of "God didn't change his mind, so we changed ours."
Back in the 1970's, when my cousin lived with her boyfriend before they finally got married, it was a HUGE scandal in our very Catholic family. Now it's the norm, most members of the next generation lived together before they tie the knot. It's actually not even that bad of an idea. Let's find out if you really are compatible before you make that kind of commitment.
The churches don't scream about this the way they are STILL screaming about homosexuality, though.