So we see how weak their argument against voting for sanders in 2016 was to begin with, then. It was that if we didn't vote for Clinton, we were helping Trump. Right, so the logic follows, then, that if they don't vote for Sanders, as he's the most popular politician in the country, let alone in the Democratic party, and has the very best chance at beating Trump in 2020, they're helping Trump.
You can already see where their loyalty lies. They've betrayed themselves and their previous criticisms against Sanders; now, they would rather rally against the most progressive politician in the country to ensure their neoliberal, corporate establishment worldview persists. They're against the people. Against Democratic voters. In favor of corporate interests and establishment politics. They would rather help Donald Trump win another victory than support Bernie Sanders in 2020. If Sanders wins, they will ultimately be proven wrong. All of their political posturing and positions will instantly become deflated and they will be wrong for the past decade. That, they can't have. That's why they're against an actual progressive like Sanders winning, even if it means dethroning an American despot like Trump.
That says enough