Well, I don't know what to tell you. I've taken several classes in political thought to get my Masters and three PhD classes on the subject. You are correct that they are not totally the same, but their fundamental core of opposition to the idea of individual rights, the concept of the State, the role of leaders of the State, their view of social society, their views on science, their concept labor..., etc. is fundamentally the same. This is not surprising because the roots of their doctrines are both traced back to Hegel. The "Old" or "Right" Hegelians eventually morphed into fascistic/nazi thought and the "Young" or "Left" Hegelians became communist thought. The "differences" you are pointing to are disputes within a common paradigm; nevertheless, they are both within a common framework. ANTIFA assumes the same biases, but adds postmodern/deconstructionist epistemology. When people don't see the commonality and don't recognize the similar core, I guess no amount of proof will be sufficient for them.