The issue isn’t a contentious primary, it’s the division and discontent sown by sore losers after the fact

That would be fine, except it ignores important context.

• This is still the Democratic primary that is being discussed. Nobody disputes that Biden is going to win, but that doesn't mean people are being somehow disloyal to vote for their candidate of choice, or for "uncommitted" to send a message to the party.

• Bernie voters overwhelmingly supported both Hillary and then Biden. Those that didn't were almost entirely right-wing voters who either mistakenly thought Bernie was a sabotage candidate, or were primarily motivated by getting an outsider candidate. There is no universe in which right wing anti-establishment voters are going to flock to someone like Hillary Clinton or Joe Biden. All of this is backed up in the exit polls.

• Hillary disingenuously scapegoated Bernie supporters for her loss to Trump, and continues to do so today. If you really feel the need to scold somebody for destroying party unity, that is where you should start. Thanks to Hillary's bullshit, the left wing of the party is understandably a bit hypersensitive to accusations of party disloyalty, and the line that you are taking is only going to exacerbate that issue.

• Right wing troll farms are all over the place trying to drive a wedge into this issue. I don't know what percentage of the loudmouthed "third party" advocates are right wing trolls, but I think it's pretty high. Feeding the trolls usually just makes it worse, but it's reasonable with reasoned arguments about that being a terrible strategy. What's not reasonable is to assume those arguments are representative of a large segment of leftists, then assume that to be the position of people discussing an ongoing primary.

This sour grapes behavior literally contributed to Trump’s win whether you want to admit it or not.

I certainly don't "admit it". Exit polling showed no significant tendency for leftists to vote against the Democratic nominee. Bernie voters voted for Hillary in greater numbers than Hillary voters voting for Obama, even including the right wing Bernie voters I mentioned above that were not a real factor for Obama. Obama also didn't piss on the left after winning the way Hillary did.

So yes, the ongoing temper tantrum

Lets talk about your language. Using terms like "sore losers", "sour grapes", "temper tantrum", and even "admit it", and also accusing people of "sabotaging democratic engagement" for literally engaging in and discussing a Democratic primary is not an effective strategy to achieve a Democratic victory. All you are doing is driving potential voters away.

This is why I view this continued relitigating of 2016, in a year where none of those participants are even running, with extreme skepticism.

Nobody in either this post or the thread leading up to this comment has mentioned the 2016 election at all. It's mentioned in other threads, but why would you bring it up here? I never said anything of the kind. However, I will say that the Democratic primary process is extremely undemocratic because it is designed to be easily manipulated by the Democratic establishment and their allies in establishment media. As long as it remains as fucked up as it is, the 2016 primary, and every other fucked up primary, will continue to be relevant.