Therein proving in itself that it cannot be that pillar of truth.
The understanding that you claim is faulty without knowledge of the Mikvah, which is what this 'baptism' IS. One would know it is not only for ritual purity (which in fact, proves the Protestant position, in so far as they know), but also for many other things. One would know. for instance, that Yeshua's mikvah was a consecration as a priest, and the start of his ministry. John knew he was not worthy to perform that consecration as a Levite.
There is also a parallel that I am toying with, but cannot yet prove - but it also could have been the High Priest's mikvah after sending away Azazel... If it was Yom Kippur, then that too can be layered on top of the consecration.
It certainly isn't about magic water.
Would there be a national cleansing for a Nation of Priests?