In what theoretical dimension do you find these “neutral interested third party” people? In my experience, every discussion is a result of (at least) two people with both an opposing view and and, more crucially, an interest to argue the point. The very prerequisite of a debate is an interest in arguing a specific point of view, which most often precludes any participant being a neutral third party.
Of course, you could always argue “for the gallery”, i.e. not try to persuade your opponent, but to merely use the debate as a platform to reach an audience. But this is not persuasion; this is rhetoric. Analogies can be used as rhetorical tools. But analogies won’t persuade your opponent.
Therefore, if you’re arguing with someone else one-on-one, and there is no one else to win over by rhetorical tricks, you should avoid using analogies, since analogies aren’t persuasive.
Of course, you could always argue “for the gallery”, i.e. not try to persuade your opponent, but to merely use the debate as a platform to reach an audience. But this is not persuasion; this is rhetoric. Analogies can be used as rhetorical tools. But analogies won’t persuade your opponent.
Therefore, if you’re arguing with someone else one-on-one, and there is no one else to win over by rhetorical tricks, you should avoid using analogies, since analogies aren’t persuasive.