I wouldn't say all of ESPN is biased against Duke. Jonathan Givony of their NBA draft team has Paolo going #1 and AJ going #6. It's just bizarre that their college recruiting guys are not talking to their NBA draft guys. It's a total disconnect between the two, which makes no sense.
As far as the college recruiting guys' bias towards UNC, they have D'Marco Dunn as the 47th rated recruit while Rivals has him at 55th, 247Sports Composite has him at 65, and the 247Sports-only rankings have him at 84th. That's a pretty wide spread for Dunn.
Dontrez Styles, for what it's worth, is ranked between in the 50's and 60's across those four rankings. There's a much tighter spread there.