Bealine,
I'm just curious where you got the info about hair colour for catholic and non catholic Irish people. Lots of scots of any religion have very dark hair. It just doesn't tally with my personal experience of Ireland.
Without going into detail, I find most of what you said a bit odd, to say the least. I am not questioning your own personal experience - I hope you understand.
I always find the sectarianism (that still exists) is an area best kept away from in forums like this, as it is very easy to offend unintentionally, regardless of your own understanding of the situation. Even acknowledged academic experts get criticised on this subject area.
As regards the general point of this discussion, I guess the big advantage of profiling is it's inherent flexibility, and ability to change rapidly in response to new security intelligence. Todays little old lady from the home counties could be next years shoe bomber (well almost!)