For those in here that take offense to this distinction:
2 party political systems function to collapse diverse political perspectives into one of two camps and normalize an 'average' view for both parties. Leftists take issue with this collapse because it erases dissenting views within each party in service of defeating an 'other' at the expense of pursuing our real political goals.
The label matters to those of us who want to make the point that the US democratic party does not really represent our interests; at-best they represent a less-objectionable flavor of the same ideological framework, but one that needs to be dismantled all the same.
"Stop trying to divide us!" is a refrain spoken by those who are better served by the party than we are.
Put another way: "We are not the same"