Why there cannot be a generic template for fair use claims

Fair use is a legal doctrine that may be used as a defence against a claim of copyright infringement. Technically speaking, until you've actually been to court and successfully invoked your claim of fair use to defend against such a suit, you're using the work illegally. In practice it's often possible to reasonably anticipate where a claim of fair use will be successful, typically by analogy with cases in which the defence has been successfully raised, and as such, the use is commonly regarded as "kosher", as it were, while still technically being illegal.

This reality raises a couple of issues. Since fair use is a defence, it's necessary to be able to explain on what basis your use falls within that defence. Since the defence applies only to particular uses of a work, you need to be able to make such an explanation for all of your uses of the work. And since claims fall into the "kosher" category by being based on solid analogies with existing cases in which the defence has been successfully raised, you need to explain the analogy you have employed, by reference to the specific fair use factors that apply to the particular work and the particular use in question.

There is no boilerplate fair use claim to be used against copyright infringement, just as there is no boilerplate claim for, say, self-defense in a murder trial, or for an estoppel claim in a breach of contract suit. Fair use claims may be very similar to each other, but that only reflects that the particular analogy being employed is strong (or at least popularly thought to be strong).

Executive summary: since fair use is a legal defence, you need to explain how it applies in every case, and this means there can be no boilerplate claims.