As somebody who spent a few years in Saudi Arabia (as well as visiting some of its fellow oil rich neighbors)...I can confirm this problem which is endemic to all rich Middle Eastern countries. As an American of Indian ethnicity (I can speak Hindi), I was able to see how people from these countries treat folks from the Indian subcontinent.
They're all basically nouveau-riche. They bring in what is slave labor/indentured servitude from poorer countries like Pakistan, India, Bangladesh, Nepal, the Philippines, etc. They clean the toilets, they serve the food at McDonalds, they build every house and skyscraper, the work the oil fields...in other words all the dirty jobs. Likewise people from western countries are brought into do the white collar work -- doctors, engineers, architects, etc....though they're having a blast.
I would say the situation is analogous to illegal immigrants from Mexico in the US -- but believe it or not we're way way way way way nicer to our illegal immigrants than these countries are to their legal immigrants! They live in terrible and barbaric conditions very similar to those described in the article. What makes it all so horrid is the disparity in wealth between the way they live and the way the elites live. If you're in Dubai, you can go snowboarding on a ski slope inside a shopping mall -- built by some guy who's in the outskirts of the city, sleeping in a hot tin can with 12 other guys, a broken AC, completely sore body, and sun burnt skin. You'll sometimes see Arab guys screaming at/assaulting these people at stores, shops, or taxis as if they're feudal lords talking to their peasants.
My father calls these immigrants heroes. They take shit (physically, verbally, mentally) you and I could not imagine just to send back the equivalent of $100-$200 a month to their families back home. That small amount of money enables them to educate their kids, feed their family, build homes, businesses, etc. They dream of the day they get to return home and finally see their families again.