I have often thought that they need to fulfill their 'random' quota by making sure they do check caucasian females. Since PAX seem to be predominantly male, fewer females will get checked. Some years ago in a London railway station I was given an official 'stop' with questions and so on. It seemed likely that they needed to balance the books of who they stopped. Which is GOOD as it needs to be truly random.
airbourne I think that any adverse remarks made by check-in staff are only read by Cabin Crew. Of course, if you were truly obnoxious - they could make a couple of phone calls to friends down the corridor!