I have no idea what you mean you when you say carpetbagger and am legitimately curious to hear your perspective.
The DNC didn't really do anything. Staff talked outside of school about him but that's it. Bernie was never a player in the Democratic Party, as he just caucuses with them, wasn't a fundraiser, and didn't stump for many other politicians in the party. He ran for the D nomination and lost by millions of votes. He didn't appeal to as many people in the primaries as HRC and he lost.
A) By and large the DNC actually adhered to their own rules.
B) Why should the Democratic National Committee play nice with someone who isn't a Democrat?
1) Everybody seems to forget that while Bernie caucuses with the Democrats he isn't actually a part of the Democratic Party.
2) Everybody seems to forget that Bernie wasn't winning. When you're the underdog, losing well doesn't get you anything.