Hindutva may be more about culture than biology but the best descriptor I can find is "völkisch nationalism" which doesn't have a good English translation ("Volk" being a more abstract idea than ethnicity but more tangible than cultural identity): the idea of Muslims as a residual contaminant of Islamic colonialism that must be excised to restore the purity of a Hindu India strongly resembles the "blood and soil" ideology of Nazi Germany which sought to restore the "birthright" of the "Aryan race" despite the majority of Germans not being considered "pure Aryans" (and declarations of "Aryan-ness" often being more pragmatic than scientific because the entire idea was based on mythology not actual history).

I could have called them fascist as many scholars agree that Hindutva should be considered a fascist ideology in its structure and application despite having no direct lineage from Italian fascism but then someone would have pointed out that "it's not actually fascism" and we could have debated that definition instead.

It's a nationalist populist movement that attempts to displace one cultural and ethnic minority it deems as invasive by empowering another it deems pure while maintaining a pretense of secularism and democracy and it does so by promising to restore an imagined historical greatness and a return to "tradition". Call it ethnonationalist or fascist, either way it would be the obvious bad guy in any piece of historical fiction. That other bad guys exist at the same time doesn't negate this point (after all, we don't need to defend 1930s/1940s Japan, Italy or Spain to point out that Germany was bad or vice versa).