It's more of a money thing. In the US, law enforcement agencies are allowed to keep and liquidate assets seized during drug raids. This generates a lot of money for the agencies, many of which have small budgets otherwise.

As far as I can tell, they care less about pot. With the exception of massive amounts of pot, they care mostly about everything else. Small amounts of pot are virtually decriminalized in much of the US, but not small amounts of other scheduled substances (I knew a [white] guy in college who went to jail during a routine traffic stop for possession of one 10 mg pill of dexmethylphenidate (a.k.a. Foculin) without a prescription -- $1500 bail).

I'm not saying police don't do racial profiling, just that the War on Drugs is not about holding a race war; it's primarily about money.