I think Perez not being a particularly effective Chairman is one issue and the BernieBros still insisting that the entire party must bend to their will is another. But they are both issues that have to be dealt with.
Why when the "moderate wing" of the party is highly mobilized or critical of others wings of the party, it's considered leadership, but when the "progressive wing" of the party does either, it's suddenly a Civil War?
There is an important question here. And I don't claim to know the answer. Should the chairperson of the DNC publicly advocate a candidate in a primary? On the one hand, Perez has just as much right as anyone else to make an endorsement. On the other, it strikes many as inappropriate, favoritizing and coercive.
And, yes, I'd ask the same question if Ellison were chairperson and he had endorsed Nixon.
Tradition is that if you're the Chairperson of the party, you don't advocate for one Democrat over another in a primary. Perez should have honored that.