I'm saying that if they are trying to rig it this way then they wasted their time. They rigged their primary but even that was a waste since Sanders had internet coverage Hillary could have only dreamed of and he still lost. Better luck next time for a truly progressive candidate. The big difference between Sanders and Trump is that most progressives care far more about issues than politicians. If we can keep Hillary's feet to the fire on progressive issues then it matters not that sanders lost. Sanders was not as much a cult of personality as Trump is.
If it is just a waste of time, then why did Sanders and Clinton fight so hard about the number of debates during the primaries and why is Sanders still bitter about having so few? Do you think Sanders, Clinton, Wasserman Schultz and others are all stupid?
You will never see a progressive as the Democratic nominee because the whole nomination process is engineered to prevent it, and you will no more be able to "hold her feet to the fire" than you were able hold Bill's feet to the fire in 1996. The only way you will ever see a progressive get the nomination is by sitting out an election, go on strike as it were, to show the leadership they can't win without you. If progressives are more focused on issues than partisan loyalty as you claim, you should have no problem sitting out this election since Trump is more progressive on some issues than Clinton is.
For example, Trump wants to rescue the children of poor families from having to go to failed, violent schools by giving them federal school vouchers, but Clinton is firmly against doing anything for but complain. Trump's plan to stop illegal immigrants from Mexico and deport those who are already here, will free up millions of jobs for poor Americans and allow wages to rise. Clinton, of course, will only talk about poor people without doing anything about it. Similarly, Democrats were firmly against NAFTA when Bill Clinton colluded with Republicans to get it passed and by renegotiating this treaty and others, Trump will keep American jobs in America and perhaps be able to bring some back. Clinton will stick with Bill's historic mistake.
In terms of equal pay for women, that has been the rule in the Trump organization for decades and it presently has more women than men in executive positions despite the fact there are more men than woman who work there. Ivanka, who is Trump's most trusted adviser has made it her mission to provide paid leave to both men and women who are new parents and to provide amenities for women who have to bring their children to work. Since Trump has been willing to pay for all these things out of his own pocket, it is clear he will fight to make them realities in other American workplaces.
So you see you wouldn't be sacrificing any of you progressive principles by sitting out this election in order to show the leadership of the Democratic party they can't get along without you, and in some respects electing Trump is the more progressive choice.