The Johannine baptism was not the same as the baptism onto remission of sins that Christian churches perform. The confusion between the two was anathemized by Trent.
Canons On BaptismCanon 1. If anyone says that the baptism of John had the same effect as the baptism of Christ,[8] let him be anathema.
Thanks for the link. I read the 14 Canons and it was very interesting. I guess there is no doubt what the purpose was there. :) The only thing is that while it said that the Baptisms of John the Baptist were different than what the Church does today, it does not say what they actually were. I'm sure that JTB baptized hundreds or thousands of people, but in Catholicism, what for? None of those Baptisms could have incorporated the work of Christ on the cross because it hadn't happened yet. How could anyone's sins be remitted at the time?