He's right, though.

"The Message" (1982) is acclaimed as the first socially-conscious hip-hop record, though there were a couple that came before it like Brother D's "How We Gonna Make The Black Nation Rise" (1980)

http://youtu.be/S-HQR2-s1J4

But most hip-hop before that was really about vacuous partying and all-American consumerism and consumption. I mean... it's not by accident by so many rappers had words like "Blow" and "Ski" in their names...