Hmmmm, complicated question.  Yes, many Qataris are to be feared.  You have enough interactions with abusive and aggressive Qataris that you learn to treat all of them very cautiously and with little trust.  It is not correct, but it is the whipped dog syndrome.  It is a small percentage, but it is a real percentage, and enough to colour your perception of the whole people.  It takes a long time to really get to know a Qatari, the safest option is to keep them at arm's length until you really know them.

 

Seriously, there are people like this everywhere, the individuals are not uncommon or unique, but the power that they have is.  Qatar has an under-developed legal human rights system and few checks on the behaviour of nationals-capricious abuses are not uncommon and word gets around.