There is no doubt from the ad I posted that you had to have a US passport, it didn't say "or". Read it carefully.
I'm not sure when your friends were hired but in the post 9-11 hiring, US passports became very important with some companies, whether noted upfront or an unofficial policy. It wasn't a problem prior to that. I can't give you details of my experience with certain applications (to protect the inside sources) but I can assure you it's a factor. Suing would be fruitless, hard to prove and would ruin your name with other pursuits. I heard about somebody who already tried that.