Let us be honest and accept there is big difference bewteen being backward and being from Low cast in Hinudim.
Hinuds from upper casts can also be poor or backward. But they dont face problems like untouchability as compare to the Low cast Hinuds.
As far as considering these Low cast Hindus as part of Hindu Nation or not well we dont doubt that. Its you Indians yourself who had alienated these low cast Hindus since long rather if you go by the history of Hinduism they had been alienated since thousands of years.
more than half of Indian Hindu population is of Dalits. These poor lowcast Dalits can not afford to have reasonble livelyhood how can these poor protest my dear.
As far as conversions. Well i guess you are not aware of the large scale conversions of Low Cast Hindus to other religions.
Earlier there were trend of converting to Islam too but keeping in mind the immense hate of Hindus towards Islam and Muslims, these poor Low cast Hindus are now more turning towards Christianity and Budhism but alas they never knew that Upper class terrorists of RSS and VHP will not leave them alive even if they convert to Christianity.