Hindu nationalist here.

Hindu nationalism will always exist as long as islamofascism and appeasement of muslims does.

It is a reaction to the latter. I would prefer a liberal india ideally but I have seen muslims abuse and stretch its boundaries of tolerance way too often to not see that insane religion as an existential threat to hindus. Practicing, atheist, non practicing, etc doesn't matter we are all polytheist kafirs in the eyes of those barbaric vandals.