Profiling risky unless large random element
My experience immediately post 911 was that the profiling was completely crazy and blatantly racist.
In a queue I was in every non-white in the queue was selected for search, no white was searched. It included a black family who were incredibly loud and american annoying perhaps but given a mum dad and two kids not much of a threat. As I was white I did not get searched myself.
The problem is that if the searches are predictable they lose any value. There are white terrorists of various types. It reminds me of my many trips to Israwl where security was tight including a long if very predictable and fomulaic interview for non-Israeli passport holders and carry on baggage X-rays but perfunctory at best for Israeli passport holders. The inevitable happened and an Israeli passport holder attempted to hijack a plane with a knife. It was noticeable after this they started having security checks for Israeli and non-Israeli passport holders which was a great relieve as I had identified it as a serious security flaw on my first trip.