How on earth can the paranoic approach cladistics have gained such widespread acceptance in biological systematics?

Cladists conflate their assumptions (ie, "coding of properties into characters and character states", actually classification) with their deduction (ie. a phylogenetic tree, also actually classification) as closely as possible, as if any assumption is correct by deduction per definition. Isn't this the shortest circularity (ie, paranoia) there is?

It is just as if I would analyze my opinions by reviewing them in the light of the evidence that made me form them. Where can such analysis lead to if not to that my opinions are correct.

How on earth have this paranoic approach gained such a widespread acceptance in biological systematics? Are biological systematists especially prone to self-confirmation?