तत्त्वप्रह्व
स्वभावस्थं निरावेशम्
Dharma is based on the vedas, which being apauruṣeya and nitya, makes dharma sanātana (more of an adj.). However, dharma is used in a much broader sense than it used to be.There's no Dharma after dissolution of this world. So how it becomes literally Sanatana?
Fundamentals such as a single supreme God, Central text, prophet (or guru of godly status) and a narrative to support their monotheism.
"Hindu" is geo-socio-cultural denomination and includes a wide variety of beliefs from absolute monotheism to pantheism to panentheism to atheism. Though there were some commonly held beliefs like karma, rebirth, samsāra, and mokṣa, their functional conception varied. Well, it may be labelled saffron, but technically Indian muslims and christians too would be hindus. There are vaidik-theists, vaidik-atheists, avaidik-theists, avaidik-atheists, vaidik-agnostics, etc, all of them still 'hindus'. Vaidik monotheism and even avaidik-monotheism cannot be identified with fundamentalism arising out of abrahamic-monotheism because the epistemology and ontology of 'hindu' monotheism is very different. I don't think one can readily equate a supreme-immanent-transcendent-with diverse forms conception of monotheism with the supreme-aloof-believe-me-else-go-to-hell monotheism.I refer to groups like ISCKON, Swaminarayan and various groups of sadhus who are raised to the level of God.
With ISCKON (don't know about Swaminarayan), i don't think it is a problem with the philosophy as it might be with the challenges that arise out of institutionalization. Nevertheless, belief in one-supreme-god and guru-parampara are as old as the vedas. Some might be outraged with idea of dialectics that forms part of various traditions, but it is this very tradition that kept ingenuity and inclusiveness alive within hindu traditions. If Buddhists could challenge popular conceptions prevailing at their time and establish theirs with credibility it was sheerly due to dialectics. I have yet to come across say, an ISCKONite, who is prepared to kill those that don't believe in his doctrine, so i feel labelling them as those with 'fundamentalist tendencies' would be inappropriate.
श्रीकृष्णार्पणमस्तु ।