Similarly , Nyaya & Samkhya were called as heterodox by HT Colebrooke.
It is high time that Rationalists aka Atheists stop parroting Ambedkar, MN Roy ,Bazaz etc , just because they were great ; it is similar to the phenomenon of ordinary Hindus (esp. middle class) parroting Gandhi, Tilak ,Vivekananda etc & thus like the latter ends up in parochial "self-pleasing" approach. Because the former are as much responsible for distorting things in the name of "reason" as much as the latter are responsible for doing the same in the name of "truth".
It is better to study actual historians & sociologists (& all ranges of them) to improve our understanding of "greys" of history & sociology before making arguments
Also the so-called "Muslim Invasion" is better referred to as invasion by "Turks" & "Mongols as majority of South Asian muslims already existed here , before they embraced Islam.