Whoever thinks those who produce hip hop aren't musicians have probably never had to program an Akai MPC or spend hours trying to track out a series of notes they hear in their head. Programming these devices is effectively the same exact thing as writing sheet music. Someone who writes sheet music is a musician, so why not someone who programs their song into a sequencer? Sounds like a clear cut case of short sighted condescension to me.
It's kinda sad that there are some who would take an elitist stance on music when the crap they listen to qualifies for the "oldies" bin at any record store. That's not to say we should ignore the classics, but lots of great music has been composed since that time. Jus' sayin'.