Far more harm is caused by the criminal prohibition of marijuana than by the use of marijuana itself.

A recent national study found that blacks are arrested for marijuana offenses at higher rates than whites in 90 percent of 700 U.S. counties investigated. In 64 percent of these counties, the black arrest rate for marijuana violations was more than twice the arrest rate for whites.
REFERENCE: J. Gettman. 2000. United States Marijuana Arrests, Part Two: Racial Differences in Drug Arrests. The NORML Foundation: Washington, DC.