Clinton won a majority, so the primary wasn't "stolen". She probably would have won without any DNC intervention, so it wasn't "rigged", either. And the DNC is under no duty to be objective, so it wasn't malfeasance in that sense.

My complaint is specifically that the DNC denied attempting to skew things to Hillary, and collected money while pretending to be neutral. Sanders repeatedly accused the DNC of favoring Hillary and attacking him, and DNC staffers said that the claims were untrue and absurd.

Priebus and the RNC openly opposed Trump, as was their right. Donors to the RNC knew that they were effectively donating to Cruz and Rubio, and against Trump. The DNC insisted they weren't opposing Sanders, and then did so behind the backs of voters and donors.

So no, I'm not mad that a party committee tried to influence a primary. I'm mad that they did so while swearing up and down they weren't, and mocking the Sanders campaign for claiming otherwise.

In light of that, if you don't believe parties have a duty to be fair to all primary contenders, then I'm at a loss. How do you expect to avoid cronyism and corruption when "private" political parties are outed working to bias primaries and you say that's okay?

Having said all that, the democratic primary election was pretty fair and the current candidate is the one who won the most votes.

Don't you think fair means, at a minimum, not doing that kind of thing? The DNC's officials were trying to persuade their own party's voters against one primary candidate and for another primary candidate.

As I understand it, a party's purpose is to organize and provide membership for people sharing whatever ideology they share, who are then (among other things) capable of signing petitions for candidates seeking to run under that Party's name. If enough party members from enough districts sign your petition, you're on that party's primary ballot in that State.

Most of what the DNC and RNC do, or what they should do, is either administrative, or attacking the other party. I'm not defending that DNC vs RNC dynamic; I think we'd probably be better off without the party system, at least as it currently exists as a privatized crony-capitalism bullshit theater with very public repercussions... and I'm also in favor of fixing the voting systems used by the States. But, in the meantime, the DNC and RNC should be banned from trying to influence their own primaries.

If DNC officials want to attack one primary candidate, they should quit the DNC and go work for an opposing primary candidate's campaign. They don't want to do that, because they'd lose the status of working under the aegis of the DNC; they'd be working merely for one candidate or another, any of which could lose.

To put it succinctly, a political party official should act in a purely administrative manner with respect to the party's own internal operation, including its primaries.

As an example, say what you want, Donald Trump is clearly not a conservative in any meaningful sense of conservatism. What is the long run result of his candidacy? there is a high probability that the long run result is irreversible damage to Republican party. Surely, party officials can act to prevent something like this, and not simply act as disinterested administrators. A political party in the US is essentially a private non for profit organization - that can run its affairs as the leadership of that party sees fit

That's the entire point.