Daniel: Slavery was legal in Christianity and in Judaism much, much before the advent of Islam. To my knowledge, there is not a single verse in the Holy Bible that speaks against slavery.
If you look back into history just a couple of hundred years. you will come across historical facts of people from the West (read Christians) raiding African countries, swooping down on African nationals, capturing men, women and children, loading their ships with the human bounty and then bringing them over to their countries where these Africans remained slaves for the rest of their lives. This went on for generations after generations with nobody ever raising a voice against this cruelty anywhere.
In all Muslim countries slavery is now illegal. What is taking place in the Middle Eastern countries which employ millions of foreign workers, is something that can termed as a "modern-day slavery." The Arabs got rich overnight when they struck oil and gas. They now have MONEY. Other nations who come to work in this region, are here just to get some of that cash. Hence, the poverty back home of foreign workers or the desire to make the fast buck, cause them accept everything their "masters" demand, This includes both you and me.
The glitter of the Riyal is just too great, Daniel, just too great!