He may not have done it on purpose, but of course "The South" is a racial dogwhistle when discussing Democratic primaries. What else differentiates Southern voters from non-Southern ones?
He and his campaign have repeated the same talking point waaaaaay too many times to be unintentional.
It's intentional and it's offensive for any Democrat to say to black voters that their votes count less than those of people in Idaho and Kansas.
So first off your OP is completely misleading. The "South" is more conservative for Dems, the whites and the blacks are both more conservative, the South is largely a Republican dominated area these days, its equivalent to a Republican saying candidate x is only winning due to the Dem state republicans being less conservative.
Write some constructive posts for a change this stuff from both sides is getting pretty old