Slavery - an unfair criticism of the Qur'an?

A recent comment on a previous post summarises many of the objections to my posts (apart from the one about not speaking Arabic...) I receive from Muslims and illustrates the ignorance of their own religion under which some poor Muslims are still labouring.
"Everyone here is babbling about something in which they have no clue. Stop taking stories and verses out of context. How exactly did you judge Islam being male oriented? When Islam came at the time of Persians and Romans none of those empires gave rights to women let alone respect of any sort to them. Slavery was in its peak. Therefore....Islam at that time announced that:1-slavery is forbidden2-women have the right to choose who to marry3-women have the right to inherit4-women were given 3 times the respect to a father by a hadeeth of prophet (pbuh)5-women participated in battlefields as a part of the army6-and in heaven a woman is a lot more beatiful than the 70 virgin hoor alaien, rewarding a women with more beauty as to what she served in life.7-the story about (hell is made mostly of women) meant to teach women not to gossip. Also, not betray, resign their husbands.
Islam gave all of that 1400 years ago when most of the world lived under horrible laws.
The elections and democracy? We had that 1400 years ago, although some ppl out of greed changed it but that is not the point.
The point is, when you take the Quran, you take it all without leaving a part of it." 
There is much to take issue with here but let us for the moment focus on #1.
"Slavery is forbidden"
The commentor blithely claims that Islam "announced that slavery is forbidden" at a time when slavery was at its peak in the Roman Empire. Really? Even my convert friend admits that the Qur'an accepts slavery as a normal, if regrettable  part of society . He tries to defend this by stressing the references to how one should consider giving slaves their freedom in some circumstances and how one should treat one's slaves fairly:
The conditions on the slave master are quite stringent in Islam. The slave must be housed decently and given the same quality of food and clothing that the master has. I have the feeling that many supposedly free employees of modern times live in less dignity than slaves have had under Muslim rule. 
We should also remember, however, that despite my friend's valiant attempts to dress up the Qur'an's disturbing references to slavery as some sort of liberal social contract, the Qur'an in fact reveals what it really thinks of the position of slaves in the infamous ayat 33:50 wherein Allah tells Muhammad with whom sex is lawful: O Prophet! Lo! We have made lawful unto thee thy wives unto whom thou hast paid their dowries, and those whom thy right hand possesseth of those whom Allah hath given thee as spoils of war (slaves). This seems to me to be a strange way of telling us that slavery is forbidden. Ah- but here I am taking words out of context again! So let's read the whole ayat:
O Prophet! Lo! We have made lawful unto thee thy wives unto whom thou hast paid their dowries, and those whom thy right hand possesseth of those whom Allah hath given thee as spoils of war, and the daughters of thine uncle on the father's side and the daughters of thine aunts on the father's side, and the daughters of thine uncles on the mother's side emigrated with thee, and a believing woman if she give herself unto the Prophet and the Prophet desire to ask her in marriage, a privilege for thee only, not for the (rest of) believers. We are aware of that which We enjoined upon them concerning their wives and those whom their right hands possess that thou mayst be free from blame, for Allah is Forgiving, Merciful.
Now I understand! It's not just Muhammad who can have sex with his slave girls without risking the ire of The  Almighty. In fact it's any Muslim...Because Allah is forgiving and merciful. (I wonder if the slave girls forced to submit to the desires of their masters thought Allah quite so merciful....)
Perhaps I'm interpreting these lines incorrectly (because I don't speak Arabic, of course). So let us go to the scholars for their expert opinion. Ibn Timiyya, inter alia, makes it clear for us: (Vol. 32, p. 89),
"The root of the beginning of slavery is prisoners of war; the bounties have become lawful to the nation of Muhammad."
And if that were not unambiguous enough, in Vol. 31, p. 380, he says this:
"Slavery is justified because of the war itself; however, it is not permissible to enslave a free Muslim. It is lawful to kill the infidel or to enslave him, and it also makes it lawful to take his offspring into captivity."
But surely we should look to the "best human ever" for our guide as to how to deal with slaves. If slavery was common at the time of the Prophet then he could have set an example for the billions of humans to come after him by NOT OWNING SLAVES HIMSELF. But wait, it seems that Muhammad, according to expert Muslim sources, was in fact a great slave owner. Ibn Qayyim al-Jawziyya, a respected scholar, in his book

"Zad al-Ma'ad" (Part I, p. 160), says,
"Muhammad had many male and female slaves. He used to buy and sell them, but he purchased (more slaves) than he sold, especially after God empowered him by His message, as well as after his immigration from Mecca.
But perhaps Muslims over the centuries since Muhammad have interpreted the evidence like my commentor and modern apologists and have done their best to rid the world of the the scourge of human bondage. That, after all, is what we would expect of the followers of a religion which apparently so unambiguously forbids it.

What then are we to make of of the fact that historians estimate that between 10 and 18 million Africans were enslaved by Muslim Arab slave traders and taken across the Red SeaIndian Ocean, and Sahara desert between 650 and 1900? Would these traders have so blatantly disobeyed their God if they believed that what they were doing was forbidden? Let us not forget, after all, that the "Christian" slave traders made reference to their holy book to justify their trade:

"Genesis 9:25-27: "Cursed be Canaan! The lowest of slaves will he be to his brothers. He also said, 'Blessed be the Lord, the God of Shem! May Canaan be the slave of Shem. May God extend the territory of Japheth; may Japeth live in the tents of Shem and may Canaan be his slave'. "

Christians traditionally believed that Canaan had settled in Africa and that thus all the dark-skinned people in the continent of Africa were there to be exploited. (How wonderful are the Abrahamic religions!) Even in the New Testament, where Jesus has many opportunities to tell his followers that slavery is a sin, nothing is heard.

Thus in all three books of the monotheistic religions - those religions deemed so much more advanced, sophisticated and civilised than their "pagan" alternatives - slavery is casually mentioned without criticism. More - the references therein have encouraged the followers of the Abrahamic religions to continue to enslave a large proportion of humanity for no other reason than the colour of their skin or because they worship the wrong god.

One final point. Many Islamic apologists assume that slavery under the Romans was far less humane than that practised under the new enlightened system of Islam.  In fact, as we are discovering with the latest research from places such as Herculaneum, slaves in the Roman Empire were generally well treated, could buy their freedom and even become full citizens of the Empire. So even the last desperate resort of the apologist - the social improvement of Islamic style slavery - holds no water whatsoever.