I cannot for the life of me find the quote you are referring to and I promise you that I'm trying as hard as can. Could you cite the speech where he made that claim?
He DID recently claim that African American unemployment is 51% - Politifact rates that as "mostly true", meaning sure, he is a politician and there's a bit of a spin on what he's saying, but the numbers are confirmed in hard research nonetheless. (It actually depends on whose research you read; Sanders got his numbers from a think tank known to be a little left wing. That doesn't necessarily mean that he's wrong or lying! It means you get to dispute the methodology of the study.)
http://www.politifact.com/truth-o-meter/statements/2015/jul/13/bernie-s/bernie-sanders-says-real-unemployment-rate-african/
Politifact has rated Bernie Sanders pretty well so far. Factcheck.org is a little more hostile to him but they still routinely rate his statements as grounded in fact.