Locke was (and still is) welcomed as an ally by theological rationalists. The Reasonableness was (and still is) attacked by theological conservatives; Locke wrote his two “vindications” of the Reasonableness in response to the conservative John Edwards, who attacked Locke’s theology as rationalistic in a book entitled Socinianism Unmasked.
... Locke fought hard for the position that people could be saved in Jesus while denying the Incarnation, the Trinity and the Atonement. In Locke’s time that would have been a reference to Socinians and deists. Supporting this “latitudinarian” view of salvation was one of the primary motives of the Reasonableness, and it was on these grounds Edwards and others accused Locke of being a Socinian rationalist. Many interpretations of these facts are possible; Locke was certainly not a deist, and I believe there’s a strong case to be made that the charges of Socinianism and rationalism were overblown and that Locke does not deserve to be called a “forerunner of deism.” However, his influence was crucial to normalizing the presence of deism in Anglican theological discourse and the eventual admission of deists to Anglican membership. ... [I]n our time as in Locke’s time, it’s generally the conservative Christians who attack Locke’s theology and the liberals, rationalists, and secularists who defend it.Viewing Founding era political theology as Lockean rational Christianity may be an alternative to Dr. Gregg Frazer's "theistic rationalism." Other notable scholars before Frazer used the term "rational Christianity" in this sense, which Frazer rejects because a theological system -- even if it purports to be "Christianity" -- that rejects Jesus as 2nd Person in the Trinity is not "Christianity." That begs the question whether it's fair to limit the definition of "Christianity" to the "orthodox." Though, that is what orthodox theologians -- from St. Athanasias to CS Lewis -- have traditionally done. It may be possible to categorize all 5 key Founders as "rational Christians" under Locke's more generous test for what it means to be "Christian."