The claim that the new IMB guidelines on baptism are nothing more than "what Baptists have always believed" is simply not true. There is ample evidence to the contrary. The historical record indicates that the influential Philadelphia Baptist Association did not require "rebaptism" of those who had been baptized in Arminian churches.
Tom Nettles documents this in the newly released volume 2 of his 3 volume work entitled, The Baptists. He describes a missionary trip taken by John Gano of the Philadelphia Association to General Baptists of "free-will principles" in North Carolina in 1754. After winning their confidence through his candor and goodwill, Gano gained the privilege examining many of the ministers on their views of salvation. Nettles writes, "Due to Gano's instruction, examination, and further preaching from ministers of the Association, the churches became Particular Baptist and eventually joined the Philadelphia Association" (111).
Their previous baptism in churches of "free-will principles" was not ruled invalid. It was acceptable to the Philadelphia Association missionaries and churches.