They could only do that by violating the party’s own bylaws and throwing out the results of the primary that Biden won fair and square. The delegates are pledged to Biden and are obligated to vote for him unless he releases them.The Dems can’t “ push him out.” He’s the incumbent…now they MIGHT choose someone else to represent the party during the convention…but I don’t think the party (either side) has chosen someone other than the incumbent at their convention.
If you’re going to accuse the other guy of threatening democracy probably best to not throw out your own election results.