It's more of a difference in practical values. At what point does the "lesser evil" itself become intolerable evil? Some people insist that you should vote for Hitler over 101% Hitler, that there is no intolerable level as long as there is a miniscule difference. Others have firm red lines in the sand, like genocide, where they advocate for abandoning them and pushing as hard as you can, even advocating for moves outside the electoral system like revolution.