Looks like there is two seperate issues that are being mixed here.

1. If it turns out that TSA can get boarding passes marked SSSS on airports prior to boarding to the US, then thats all on them.

2. If you have a non-working laptop (or other deivce) and can't demonstrate it prior to boarding then you are very unlikely to get to bring it on board from any sensible airport.

Have I seen an of this in DOH or any other airport? Yes, #1 you see all over, there's even a forum on FT dedicated to the TSA/CBP and all related fun. As for #2, yes, I've seen it and it generally is a good thing, if you have a look at some past issues with safety.

Could the security staff at DOH have handled it better? Likely.

Is your impression of QR customer service accurate? Your descriptions sounds par for the course.

(And your projections on what you are entitled to as a white caucasian and how security is related to wether you can be linked to the middle east in any form, I can only say it's always a tad funny when it happens this way.)

-A