A "god" is the prosopopoeia of a written or verbally passed-down system (or the personification a general concept, as in the case of many Greek deities).[*] Any "proofs" thereby would still rest upon consistency with the religion's standards.
In mathematics, a new theorem is proven by demonstrating its coherence with the applicable system or that it can be deductively derived from the latter's axioms / pre-established statements (certify that the proposition is a consequence of them).
(1) Thus to be accepted as something more than just an arbitrary add-on, an Asparagus Man (of that British Festival) would need to be validated as either compatible with the religious canon's accepted ideas / tenets; or substantiated as falling out of them.
(2) To be officially disapproved -- rather than merely arbitrarily rejected, an Asparagus Man would need to be demonstrated as incompatible with the religious canon's accepted ideas / tenets. The latter would still seem to exclude Asparagus Man even if it was possible for a perverse product to emerge from later stages of a school of belief's developing statements. (Akin to smut being an undesirable novelty arising in corn crops, or at least when the fungus is not deemed a delicacy as in Mexico).
As a precedent: Halloween also lacks direct Biblical footing (even Christmas for that matter), and yet
has apparently been approved by the Church of England (but probably not all Anglican institutions worldwide). Which still does not mean or negate the possibility of Halloween having indirect compatibility with Biblical or church doctrine.
But should there be no appealing to or an analysis of Anglican canon transpiring here at all in either the case of Asparagus Man or the other (October holiday), then for the time being their acceptance / rejection by whatever applicable parties can be judged as arbitrary.
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[*] Immanuel Kant: Reason inevitably creates objects for itself. Hence everything that thinks has a God. [Or some equivalent sacred, synoptic symbol representing certain formal expositions.]
[...] In moral-practical reason, there is contained the principle of the knowledge of my duties as commands, that is, not according to the rule which makes the subject into an [object], but that which emerges from freedom and which [the subject] prescribes to itself, and yet as if another higher person had made it a rule for him. The subject feels himself necessitated through his own reason (not analytically, according to the principle of identity, but synthetically, as a transition from metaphysics to transcendental philosophy) to obey these duties. What God may be can be developed from concepts, by means of metaphysics; but that there is [literally] a God belongs to transcendental philosophy and can only be proved hypothetically. --Opus Postumum
. With the track record of clergy over the years, this is not entirley out of the realm of possibility. The fall of asparagus to the level of unclean organisms is a perfect example of how myths are established. Answer: It's us and the trust we have in the guardians of the belief. I wonder what the pig or someone dressed as a pig did centuries ago to earn the same distinction. 