Thanks, that's almost what I mean, but I might modify your examples slightly. They're good examples to work from lol (I'm pretty bad at coming up with scenarios that fit what I'm talking about). Sorry if this sounds kind of crazy:

Jess wants to draw a picture of a bird. For this, since Jess is completely broke and homeless, she would need to rob an art store to get art supplies. (Let's say for sake of example that there is genuinely no other way for her to obtain art supplies to draw the picture). Jess justifies this act of robbing the store in order to draw her bird picture because there's no other way she can make the picture otherwise. She makes the claim that robbing the art store is necessary in absolute terms, while overlooking or ignoring the fact that drawing the picture of the bird isn't necessary in the first place (even though she might desire to draw it, she doesn't need to, and therefore doesn't need to rob the art store, either).

Or...

When Alan plays tennis, his knee hurts. Alan has a strange condition that his knee only hurts after he plays tennis. When his knee hurts, he has to put ice on it, which requires an expensive refrigerator with an ice machine since that's the only way he can possibly get a good supply of ice in his situation (hypothetically). Alan then decides to buy the expensive refrigerator with stolen money from his grandma, and claims that it's an absolute requirement for him to, without considering the fact that he doesn't actually need to play tennis, though he might want to.

In both cases, someone is claiming that something (an action, state, etc) is necessary overall, because it's part of a larger goal/endeavour; without addressing the reality that it would only be necessary as a component of that larger goal that it would be in service of, if that larger goal was necessary, which in fact it isn't (and therefore neither are any components that would be required to achieve it).

I hope this makes sense :)