Is "That was then" a reasonable excuse?

This post is more of a rant, I suppose, then anything else. The subject is this: Is it reasonable for defenders of Old Testament (the Hebrew Bible) to say that God authorized certain behaviors that we reject today because "That was then"? The answer is clearly no.

Let's list some examples:

1. You could own slaves--as long as it wasn't a fellow Israelite. (Lev. 25:44-46)
2. But you could own Hebrew slaves (Contradiction!). But you could own him for only 6 years. (Exodus 21:2-6) BUT if you gave him his wife and he had kids, they were to remain slaves FOREVER.
3. Note that the above doesn't apply to females. They never go free, apparently.
4. You can sell your daughter into slavery ... and she could never go free. (Ex. 21:7-11) The owner could choose to marry her--presumably against her will. If he takes another wife, that okay as long as he continues to feed and fuck her.
5. You could beat your slave and if he didn't die after a couple days, that was okay. (Ex. 21:20-21)
6. If you discovered that your wife wasn't a virgin on your wedding night, you could stone her. Deuteronomy 22:13-21. It should be noted that the text says, "if tokens of her virginity be not found", suggesting what? That's right. Hide the evidence and be freed from an unwanted wife.
7. Genocide. E.g., Numbers 31.

The Old Testament, as far as I know, doesn't specify how the stoning is carried out. However, according to the Wikipedia article on stoning (link), these were the conditions specified by the Islamic Penal Code:

Article 102 – An adulterous man shall be buried in a ditch up to near his waist and an adulterous woman up to near her chest and then stoned to death.

Article 103 – In case the person sentenced to stoning escapes the ditch in which they are buried, then if the adultery is proven by testimony then they will be returned for the punishment but if it is proven by their own confession then they will not be returned.

Article 104 – The size of the stone used in stoning shall not be too large to kill the convict by one or two throws and at the same time shall not be too small to be called a stone.

Imagine this. No one rock can kill you. Various of your teeth chip. An eye is blackened. Another eye is burst from its socket. Ribs are cracked. Maybe your ear is shredded. An eardrum bursts. Eventually you have a concussion and perhaps nausea sets in. You soil yourself. You vomit. If you are lucky, you become unconscious. If not, you'll probably die in even more pain while you bleed internally.

I think this might be the single most inhumane of killing another being. Christians are fond of saying that crucifixion is the worst. But at least once the nails are in, it's just a matter of waiting.

The point of this post isn't the various evils of the Bible but rather whether any of the above can be justified because of the times in which the original so-called recipients of the law lived.

We are supposed to believe that this horrific law was handed down by a benevolent god. This god is also, traditionally, all-knowing and all-powerful.

How is it then that this all-knowing, all-powerful being cannot make known to his followers a better way of doing things? How is it that we are told that the kosher laws were perhaps given to specify a humane way of killing beasts and yet we cannot have a humane way of killing people, supposing that a death penalty is required at all? Speaking of which, how is it this god who was in more-or-less direct contact with his people couldn't have explained how to carry out justice without a death penalty? Why could not this god make it clear how people could be rehabilitated? How about a method of agriculture that doesn't require slavery? Even supposing that we cannot imagine how, in that society, to pull it off, remember we are talking about a omnipotent, omniscient god.

I've heard this argued before, that God had to allow slavery because of the times. That there had to be stoning because they needed a death penalty.

Given the traditional Abrahamic god, this is patently false. Even allowing a god that too was learning as it went along, that god is unbelievably unimaginative (except in matters of cruelty).

The god of the Old Testament is grossly incompetent, evil, and even stupid.