Your argument makes no sense.
You acknowledge progressives won’t vote for moderates. But what makes you think moderates won’t vote for progressives if they don’t have a choice?
Do you really believe the people who voted for Clinton wouldn’t have voted for Sanders in the general? If so, then shouldn’t the blame be on them too? If not, then can you admit you’re wrong?
I recommend setting up logging in yourself so you can see why you’re wrong.