He's being just as gracious as the Clinton campaign was at this point in 2008.
Even if the two were in any way comparable (they're not), the key difference is that Hillary was solely fighting her opponent, Obama, while Bernie is fighting basically everyone who doesn't kiss his ass, actively working to block unity and trying to destroy the party's chances in November.
He really isn't. All he wants to do is make the process more open. Clinton did more damage to Obama and party unity with her pseudo-racist campaign in 2008 than Sanders has even come close to this year.
I don't know how you got a master's degree when you're incapable of understanding that Sanders' claim that the party is out to get him, doesn't care about his supporters, and helped Hillary win by cheating, is far more damaging to party unity than Hillary's claim that she was more prepared for office than Obama.
Wow dude, really? Is that necessary?
Saying that the party establishment is against you, wanting to open up the primary process, and getting big money out of politics is not as bad as the racist undertones of the 2008 Clinton campaign.
Could he do a better job had reprimanding his crazy supporters when they get out of line, totally. Yet I think we forget just how nasty things got towards the end of the 2008 campaign and how little the Clinton folks did to reprimand their crazy supporters as well.