"Perfect analogy" fallacy
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Original Question
The website Philosophy News has some entries on logical fallacies, and this one stood out to me. It's the reverse of the weak analogy - in that fallacy, two things are said to be analogous, but they are not really like each other. In this fallacy, the analogy is rejected for not being 'good enough', with the implication that in order to be good enough, the analogues have to be identical. This however, would make any comparison pointless - it's like comparing the letter A to the letter A!
E.g.
Jessica: If we regulate car ownership in this country, then we should regulate guns.
Harry: But a gun is a gun and a car is a car. You can't compare those two things; they're different.
Although this might not qualify for an entry in its own right, it could be added under weak analogy.
Comments on Question
I have seen this used many times when it makes sense. Typically, it is when people are, as you said, offering weak analogies. I have a difficult time seeing this as a fallacy. It seems more of a lack of understanding of what an analogy is and how it works. We have seen this with the "you can't compare covid to the flu" people. Of course you can! What one can't do, is claim two things are similar when they are not. So when people say "You can't compare X with Y" I really think they are just not being precise with language. They really mean that the comparison made was weak or perhaps there are so many differences (or differences of such significance) that the comparison is pointless.
Answers
2Harry and Jessica are talking past each other and will not communicate at this rate. Harry should ask Jessica for the premises she uses to come to her conclusion. This is poor communication.
Perhaps we could tweak the definition of argument from fallacy because what I understood from the article, is that perfect analogies sometimes proceed with a fallacy fallacy. We might not have, however, a fallacy in the original argument. Instead, the fallacy is "appended" by the person committing the perfect analogy fallacy, and then proceeds to argue from fallacy.
Example:
Person 1: You shouldn't drink too much coffee. It might be harmful to your body. Would you really drink soda every day?
Person 2: Coffee is not like soda. I'm gonna continue with my tenth cup.
Identify the principle: unrestrained intake of any kind of drink is harmful to your body.
Has this principle being rejected by person 2? If the answer is no, then that person has committed a perfect analogy fallacy. Moreover, since person 2 went ahead with the decision, he/she also committed a fallacy fallacy. This is done, however, by appending a fallacy to the original argument.
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I agree that it should be mentioned because people use that kind of objection to play it dumb. It's like strawman in a sense that they purposefully misinterpret what is being said, i.e "analogous or equivalent" to being "equal". And even when you explain the difference between "equivalent" and "equal", they stubbornly refuse to acknowledge the analogy and usually they respond again with the phrase "No, they're totally different" and also may follow-up with another strawman. So I think it should be added. Usually it's not just poor communication or misunderstanting. It's either intentional, in which case it is a fallacious tactic or when it's unintentional that means it's a fallacy that confuses them, so why not include it?
Thank you Rationalissimus of the Elenchus for bringing this up! I had never heard it, didn't know it had a name, but I've dealt with it many, many times from people who just wanted to continue to believe what they were believing and ignore the contradiction in their thinking. Just another tactic to hide their denial.