Logical Fallacies: The Weak Analogy

AZU hasn't been discussed here much any more. Quite frankly, they are no longer relevant, though they flounder with the same playbook like a noob Madden player who picks the Hail Mary pass over and over again. But they make plenty of good examples for studying logical fallacies.

Today's lesson is known as the "Weak Analogy:"


AZU argues because so-called "hard-core pedophile activists" and sex offender reformists share some common goals then they must be one and the same. The Black Panthers and Martin Luther King both shared some common goals like the eradication of discrimination against African-Americans, therefore MLK was a militant racist thug who believed in killing to get what he wants, right? According to AZU logic, the answer would be yes.

I don't follow NAMBLA, but facing the same general direction does not make "pro-pedo" groups and SO reformists the same. The terms pedophile and sex offender are not mutually exclusive terms, and the two groups are not mutually exclusive.

It is entirely possible for someone with ulterior motives to join a group contrary to their status in life. For example, Absolute Zero United has two repeat sex offenders in their dwindling group. 

More on this fallacy below.

Weak analogy

Definition: Many arguments rely on an analogy between two or more objects, ideas, or situations. If the two things that are being compared aren't really alike in the relevant respects, the analogy is a weak one, and the argument that relies on it commits the fallacy of weak analogy.
Example: "Guns are like hammers—they're both tools with metal parts that could be used to kill someone. And yet it would be ridiculous to restrict the purchase of hammers—so restrictions on purchasing guns are equally ridiculous." While guns and hammers do share certain features, these features (having metal parts, being tools, and being potentially useful for violence) are not the ones at stake in deciding whether to restrict guns. Rather, we restrict guns because they can easily be used to kill large numbers of people at a distance. This is a feature hammers do not share—it would be hard to kill a crowd with a hammer. Thus, the analogy is weak, and so is the argument based on it.
If you think about it, you can make an analogy of some kind between almost any two things in the world: "My paper is like a mud puddle because they both get bigger when it rains (I work more when I'm stuck inside) and they're both kind of murky." So the mere fact that you can draw an analogy between two things doesn't prove much, by itself.
Tip: Identify what properties are important to the claim you're making, and see whether the two things you're comparing both share those properties.