Quoting kilobug:

it's often very difficult to use knowledge or understanding given by rationality in a discussion with someone who isn't versed in the Art

From what I understood these analogies are meant to better explain some basic point to people with little to no previous background. I assume that the average target of these analogies has never quite considered your objection, and is sitting on a lower level, so the analogy should be good enough to deliver the point. Once you've made yourself clear, you can then explain to your interlocutor that the analogy is not an isomorphism.

This is at least how I usually proceed when trying to explain new and complicated concepts to people that encounter them for the first time.