Often analogies can be good ways of communicating. If it is raining heavily I could say “it’s raining heavily” or perhaps I could use an analogy “it’s raining cats & dogs”. This a perfectly reasonable use of analogy to underline the point I wish to make with perhaps greater force and imagery.
However, analogies are sometimes used as evidence to support the credibility of a particular argument. For example, during the cold war. It was stated that the Vietnam war was defending other south-east Asian countries from communism. It was preventing the other countries from “toppling like dominoes” and the Vietnam war was the “thin edge of the wedge”. Two graphic analogies, but are they, in any way, evidence to support an argument to fight the Vietnam war?
Were the analogies any good? Were the other countries likely to all succumb to communism? Or was the imagery of the analogy masking the lack of evidence? Where was the evidence that communism would extend into the other countries? Analogies reinforce an argument with no additional evidence. They are empty rhetoric.
In the event, after the USA lost the war in Vietnam, the other countries did not all succumb to communism. Even, at the time, if the analogies were closely examined, it would have revealed little evidence to support the Model that losing a war in one place would influence, in a decisive manner, the outcomes in another place.
If a proposition is supported by arguments from analogy, then ensure the analogy holds and is fully appropriate. We must ensure that underneath the analogy there is more credible actual evidence, and that the analogy does not mask a lack of any evidence.