That post you're confused by and several others are little more than a self-styled cognoscenti flailing about in an effort to maintain the appearance of intellectual and moral superiority over the unwashed masses on this board. Since it's a largely left-leaning place, the fights must necessarily occur between groups both on the left for who is the best of the left. After all, the right isn't present to engage and attack, so new enemies must be found to triumph over.
Bernie Sanders and his supporters are a nice enough proxy demographically for the right as you can find on the left, so here we are. This is merely Round 321.
Mercifully it will end once the primary is over.
Let nothing stand in our way of identity wars! If we don't have enemies, we'll have to make new ones to attack!