Being an ex-Christian humanist too, I recognize the feeling that Hindu polemicists are "mad dogs". They don't know the issues, can't tell friends from enemies, and don't have elementary manners. This is all true.
However, I'm afraid your view of history is informed by modern writers on history rather than on the ancient facts. For instance, there never was a time when the majority of Indians "threatened" to become Buddhists, let alone Jains. The Buddhist Sangha recruited exclusively among Hindus; of most of them, we know the caste, and the immense majority of Buddhist philosophers was of Brahmin origin. Buddhism was just a Hindu Sampradaya among others, continuing the worship of the Vedic gods and even taking them along to e.g. Japan. The notion of Buddhism as a separate religion is due to the early Orientalists who discovered Buddhism in East and Southeast Asia and gave it a name before discovering its Indian origin. It is a hilarious "secularist" invention that Buddhism in India was "wiped out" by Sanatana Dharma; that was well-documentedly done by Islam. Buddhism had then flourished in India for 17 centuries under Hindu rule, and created large institutions which the Muslim invaders burnt down.