I believe you are missing the forest for the trees. First, I acknowledge your examples are separate ideologies.
That concept also applies to the right... social conservatives, right-libertarians, and neoliberal ideologies are equally separate. However, those practitioners have no qualms about banding together to suppress dissent (or until such time they are the only voices).
Where the left leaning practitioners are unable to do so, they will be forever tyrannized by the banded majority.
To put it more succinctly, the enemy of my enemy is my friend (when freedom is on the line).
K.