While some proponents of Secular Buddhism have disclaimed Buddhist modernism (for example, Higgins, here), much in fact seems to remain the same. Not only was the idea of an original Buddhism located in the Pali canon formulated by European proponents of Buddhism in the nineteenth century (Lopez, The Scientific Buddha, 104), but so also was the idea of separating the Buddha from Buddhism (Lopez, From Stone to Flesh, 169).
Both of these ideas, focus on the Pāli canon and a Buddha freed from Buddhism and Buddhists, inform the program of Secular Buddhism proponents. The focus on “the historical Buddha,” that is, Śākyamuni as a human being, one who was born, lived and suffered, grew old and died, but who in the mean time taught a doctrine of liberation from suffering, remains a central point of faith for Secular Buddhists—despite these ideas being formulated by Europeans in the nineteenth century. (Perhaps that explains Stephen Batchelor’s interest in the work by W. Woodville Rockhill, which dates from 1907, and his apparent neglect or perhaps ignorance of more than a century of scholarship on these issues. See, again, the Insight Journal interview.)
Two considerations, however—
1. Context. Emphasis on the Buddha as human does originate in modernist Buddhism. What needs to be considered in addition, however, the context of that emphasis. In the nineteenth century (and even into the present), many Christians asserted the superiority of Christianity on the grounds that it is the only religion whose God was (is? sorry, my theology is too weak to figure out the grammar here) human. Jesus Christ was born as a human, and they claim, no other religion has had a human god. Thus, one form of resistance to Christian missionaries in the nineteenth century was to assert the human status of Śākyamuni. In other words, the human Buddha originates as a polemic device.
2. Significance. To the extent that it can be established, the actual historical existence of Jesus provides no grounds for accepting the religious claims of Christianity, such as the divinity of Jesus himself, and so on. Similarly, to the extent that someone (Batchelor, or the much more highly qualified Nakamura, or Ñanamoli, or Schumann, or the disastrously awful Armstrong, or Hanh, or Kalupahana) could establish the actual historical existence of Śākyamuni, that provides no grounds for accepting the religious claims of any form of Buddhism, including Secular Buddhism. These are three different realms of discourse: historical, Christian theology, and Buddhist thought.
So, the questions that then emerge are:
Why bother? There is no need to establish parity with Christianity in this now quite outdated way.
So what? It does nothing to confirm or deny the validity of the teachings.
It would seem that the third reasonable question to ask at this point is, Who cares? Evidently Batchelor and other proponents of Secular Buddhism do—though I suspect that they only care to the extent that the historical Buddha they concoct can be used to give legitimacy to what they already believe.