Omg, wow. Democratic leadership wanted the candidate that had helped build the party and contributed to other Democrats across the country in election efforts for decades rather than the man that sued the party, called them all entirely corrupt, and only changed party registration to be a Democrat 3 months before the first caucus only for legibility purposes? Amazing. Who would have thought?
Democratic leadership wanting Hillary over Bernie doesn't change the fact that they outwardly did nothing to discredit his candidacy. They didn't vet or attack him. They didn't derail his legitimacy. They just simply didn't like him. If you expect 100% impartiality from politicians, or any human being, you're living in a different world than I do. Everyone has biases. But, they didn't outwardly act on them in a way that it would affect voters. Now, if you want to complain about reported super delegate commitments before the first contest, sure. But, Obama still broke through that in 2008.
At the end of the day, Hillary fairly won the primaries by all measures. The DNC leadership having a personal preference that they didn't announce to the country didn't change the fact that Hillary had a very comfortable victory against Sanders in the primaries.