While the dalits who were at the bottom of earlier castocracy and brahmins who are now at the bottom of the post-periar inverted castocracy, both of them know what it is to be illtreated, no wonder if they come together now, when given a chance by BSP.
But, there is also probably a deeper reason. Whem islam attacked and subjugated India, the kshatriyas, as per caste-dharma, fought and died; the vysyas ran off from the villages with their gold and jewels and came back later. Sudras simply took wage-work under the new moslem masters, but retained their lands, hindu gods and temples. The pre-moghul dalits were forced to convert to islam. But the brahmins did nothing, just waited to be killed; even moslems found it difficult to handle such passive resistance; they simply forced the learned brahmins into ghettos called agrahaarams [garlands] around temples and the others out of the villages as the new dalits. This explains why the dalits retained god-related names like jag-jeevan-ram, khansi-ram, krishna-swamy etc. to this century, while the OBCs went for modern names. Perhaps, this made Gandhiji call the dalits as harijans, Dr. Ambetkar marry a brahmin. In fact, the caste system which seems to have saved hindustan alone from being wiped off their old religion, unlike in persia, indonesia etc., may also now help save the country from selfcentred political parties of crminal greedy politicians, riding mainly on minority antinational votebanks.