Hinduism fundamentalism is very antagonistic to Christianity, as well, as they see Christianity largely as the religion of colonizers. But even when dealing with pre-colonization Christianity in India, Hindu fundamentalists view Christianity as a "foreign" religion. Christians in India are subject to abuse from Hindu fundamentalists, although on a smaller scale than Muslims largely because there are about 6x as many Muslims as Christians, leading to Muslims "fighting back" more often.
Hindu fundamentalists view on Buddhism is a little more nuanced, as Buddhism is an offshoot of Hinduism. In that regard, Hindu fundamentalists tend to view Buddhists as more of an "errant child" to be corrected than one to try to wipe out/remove from the country altogether. There are instances of sectarian violence against Buddhists when Buddhists refuse to be controlled by Hindu majorities.
Hindu fundamentalists also have a fairly nuanced view of Sikhs and Jains, as well, as both are native Indian, but non-Hindu, religions. As with Buddhism, there isn't the idea that these religions are "foreign invaders" as with Christianity and Islam. However, as these religions are not Hindu offshoots, they are seen as "improper" Indian religions which are not acceptable for a unified India under Hinduism. Of course, as Jains are pacifists and Sikhs only believe in violence as a last resort in self-defense, it's a bit harder to engage in mutual violence with these groups. However, there is a history of anti-Jain and anti-Sikh violence in India, although it is more common for these groups to simply abide their oppression because they are fairly numerically small and know they do not stand a great chance of benefitting from violent responses.
In short, a basic tenet of Hindu fundamentalism is that India is a Hindu country and that all "real Indians" should practice Hinduism.