Problems arise when the targeted class belongs to a politically sensitive group, especially if it is a racial group other than white. If the police check out a slinky white woman who keeps approaching men in the bar of a classy hotel, she may turn out to be promiscuous heiress, which it isn't illegal to be. She raises Cain because she has been humiliated. What usually makes the news is profiling of blacks. The fact is that most street-level drug dealers in Washington are black.
Blacks are heavily involved in transportation of drugs for sale.
Should you doubt this, ask any cop of any color. Dealers look and behave in certain ways, and are certain kinds of people. They are black, scruffy, young, hang in certain places, display certain body language when cops are around. So cops check them out. The downside of profiling is that, while young black males on I95, wearing scruffy clothes and driving rentals with no baggage, are in fact often drug couriers, often they aren't.