In your opinion. An opinion you're no more willing to budge on than the leftist is willing to compromise their position that any further concession to the right is tantamount to endorsing their atrocities. That someone willing to "reach across the aisle" at this point is doing little more than consenting to crimes committed in their name. The leftist and the liberal are standing equally on their beliefs and their principles, and both are just as unwilling to compromise. Can you truly say either one is more responsible for dividing the opposition to the fascists than the other? If you truly believe that voting for anyone but Trump is worth whatever price it takes, then you also believe there's no harm in endorsing a more left leaning candidate no? Unless you truly believe more Democrats are willing to permit crimes against humanity than there are leftists willing to find an acceptable compromise. If that's the case, the United States of America has already fallen too far to save.

But when it comes to the general, the most milquetoast corporatist democrat is better than right-wing outright fascism.

Only if you only care about the short term. And then short term thinking is what has got us to this point.