False equivalence

False equivalence is a logical fallacy in which two completely opposing arguments appear to be logically equivalent when in fact they are not. This fallacy is categorized as a fallacy of inconsistency.

Characteristics
A common way for this fallacy to be perpetuated is one shared trait between two subjects is assumed to show equivalence, especially in order of magnitude, when equivalence is not necessarily the logical result.[2] False equivalence is a common result when an anecdotal similarity is pointed out as equal, but the claim of equivalence doesn't bear because the similarity is based on oversimplification or ignorance of additional factors. The pattern of the fallacy is often as such: "If A is the set of c and d, and B is the set of d and e, then since they both contain d, A and B are equal". d is not required to exist in both sets; only a passing similarity is required to cause this fallacy to be used.

False equivalence arguments are often used in journalism and in politics, where the minor flaws of one candidate may be compared to major flaws of another.

Examples
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The following statements are examples of false equivalence:

(the "equivalence" is in factors that are not relevant to the animals' suitability as pets).
 * "They're both living animals that metabolize chemical energy. There's no difference between a pet cat and a pet snail."

(the comparison is between things differing by many orders of magnitude: Deepwater Horizon spilled 210 million US gal (790 million l) of oil, your neighbor might spill perhaps a pint.)
 * "The Deepwater Horizon oil spill is no different from your neighbor dripping some oil on the ground when changing oil in his car."