I can't blame Qataris alone for the whole discrimination /caste system witnessed here in many levels.
Because of my job, I got to witness in daily bases how expatriates also exploits other expatriates.
From Indian managers exploiting their Filipino / Nepali workers to lebanese exploiting their Egyptian/ Syrian workers. 
It's really sad that the current system does allow that. 
Qataris are not the only  culprits. Many of those sponsors has couple of hundred workers under their sponsorship. Most never visited their own workers accommodation or knows the wellbeing of the workers.
As much as I hate justifying that, but the family day policy has both security & cultural aspects . In a country where gender mixing is still considered a taboo in the mindset of it's people, being crowded out malls two years ago in weekends & public holidays because of army of workers certainly had them demanding the implementation of such policy