Profiling would be great if it worked. But the insaniacs only have to sneak one corn-fed, blond-hair, middle-America, converted Jihadist through security to break the profiling security barrier. Profiling is too easy to predict.
In theory you are correct--there is no guarantee that blonde, blue eyed moslems can not be terrorists.
However, with the exception of the English-convert shoe bomber, ALL the attempted and successful terrorist attacks were by people of Arabic ethnicity--and almost all being male, between the ages of 18 to 45.
So to say ethnicity is not one (major) indicator of the possibility of being a terrorist is politically correct nonsense.