1) I find it interesting that this person's idea of an "ecumenical answer to the question of baptism" is to exalt so-called "believer's baptism" at the expense of the majority position of the Church Universal.
2) John the Baptist did not "introduce" the rite of baptism. Jesus himself said of his own need for baptism (surely not for an example, since he was 30 and not newly 'believing'; nor as a sign of repentance, since he was sinless) that it was "fitting for us [Jesus and John] to fulfill all righteousness" (Matt. 3:15). The rite of baptism extends back into the Old Testament, as both ritual purification and ritual ordination, as Numbers 4:1-3: "Then the LORD spoke to Moses and to Aaron, saying, 'Take a census of the descendants of Kohath from among the sons of Levi, by their fathers' households, from thirty years and upward, even to fifty years old, all who enter the service to do the work in the tent of meeting."
3) Christian baptism is not a baptism of repentance. The dual command, "Repent and be baptized" would make no sense if repentance were intrinsic to the meaning of baptism. Acts 2:38-9 gives the meaning of baptism as directly related to the pouring out of the Holy Spirit: "Repent, and be baptized for the remission of sins [because of the remission of sins], and you will receive the gift of the Holy Spirit."
Last, the argument for Antipedobaptism seems to center on the fact that regeneration and infant baptism are not one and the same. But this is not true of "believer's baptism" any more than it is of infant baptism. Infant baptism takes baptism to be an external "sign" of an inward grace, and a mark of inclusion into the New Covenant. "Believer's baptism" (as the view that only the regenerate should be baptized) takes baptism to be an external identification with Christ, which also has nothing to do with the "coterminacy" (as the author puts it) of regeneration. Infant baptism supposes regeneration in the future; "believer's baptism" supposes regeneration in the past. (Again, I use "believer's baptism" to indicate the beliefs about baptism that come with believing that the regenerate are the only proper candidates for baptism. Even in the pedobaptists' minds, there is validity to the baptism of someone who was not baptized before--for example, as an infant--and who recently has become a Christian.)
I just think it is so neat when religious people find it necessary to correct God.