There’s two big reasons why racial profiling is crap – and I’m not going to bore you by pulling out some ideals about “racial harmony” and how we should all just get along. You don’t have to. Racial profiling is a bad policy, and justified by crappy logic.
Racial profiling is bad security and policing policy. There is no reason to think that criminals, terrorists, or drug dealers are stupid. As soon as we concentrate law enforcement towards a specific group, the “bad guys” will change tactics. In fact, the smart and effective bad guys will do this – and the only ones we’ll catch are the dumbasses. A large number of the “terrorists” we’ve caught inside CONUS fall into this category, with barely workable plans (if they even had plans). This makes me worry that while we were chasing these idiots, the competent ones are working off the radar.
Racial profiling is justified by crappy logic. For example, my new mayor talked in May about how “certain groups”  tended to be arrested more, and so justified racial profiling as being a necessary evil.  But that’s a logical tautology. We’ve known for a while that drug usage in many categories is roughly equivalent among whites and blacks, but arrests and convictions are strongly skewed towards blacks.  So think about this for a second. If we’re focusing our police efforts towards any group of people, we’ll see more arrests and convictions in that group of people. Which then is used to justify concentrating our policing efforts among that group of people… yeah. You see how this is a never-ending cycle that doesn’t actually address the real problem of crime.
There’s more reasons why profiling is crappy for our society – for example, how it causes profiled groups to distrust and not cooperate with law enforcement – but these two alone show how racial profiling actively undermines our security and produces its own false justification.
 I’m paraphrasing. The original is here.
 I am strongly simplifying.