"X is bad, therefore Y is good": what is this fallacy called?

This is such a simple fallacy, but for the life of me, I cannot find the name for it.

The more complex version of the fallacy I'm talking about is where a person claims that X is bad, and because it's bad, Y (Usually the opposite of or on the opposite extreme end of the spectrum that X is on, and is usually as bad as X but for different reasons) therefore must be good. This fallacy seems most common in political situations.

This is the most basic example I can think of: "Nazis are bad, therefore, communism is good"

Thanks in advance

I have never heard of something like this before, so I would just assume a non-sequitur(it simply does not follow that because X is bad then Y is good).

As for the idea that if the X is bad, then the opposite of X must be good, I see no problem with that reasoning. This is really just a tautology: assuming the two words we use are actual opposites. However, if bad is simply a characteristic of X, and it has multiple characteristics, then it would have no logical/literal opposite. The "opposite" would be a short-hand, casual way of saying "very different from." For example, "Bill is quiet, and Tom is the opposite—very loud." Tom is not a literal opposite of Bill (Tom still has a penis and not a vagina, Tom likes action movies just like Bill, They both like runny eggs, etc.)

Another way to look at this is through the false dichotomy. By saying "Nazis are bad, therefore, communism is good," there is the false assumption that a) communism is the "opposite" of Nazis and b) that there are only two choices and we must choose the lesser of the two evils.

Hope this helps!

Could this be a variation of Appeal to Desperation?
- X is bad
- something must be done
- Y is not X,
- assuming Y is better than X
Therefore, Y must be done.

This should be a fallacy, perhaps its own fallacy. It is the central fallacy of 'humanitarian' war, where the 'good' intervention kills way more people than the 'bad' leader.
Seems similar to a false dichotomy, but not quite.

I think it depends on what X and Y are.

1. Fallacy of bifurcation or taking it to the extremes: Overeating is bad. Therefore starvation is good.
2. Appeal to common belief: A lot of people believe that eating a banana a day is bad. Therefore not doing that is good.
3. Fallacy of equivocation and negating the antecedent: Not doing your homework is bad. Therefore, because Jimmy does his homework, his grades are good.
4. Ad Hominem circumstantial: The entrepreneur said that not donating money to his non-profit is bad. Therefore not donating money to his non-profit is good.
5. Fallacy of Ambiguity (example 3 also fits this one): What Mary did is bad. She shouldn't have arrived that late. Therefore, it is good that she finishes her dinner first.

Explanations:
1. This one offers only two choices; overeating and starvation. I would dare to say that a true healthy life-style is somewhere in the middle.
3. The first part refers to building a bad habit. Perhaps Jimmy is taking a class were the assignments are not required but suggested. The second part uses the word 'bad' as in the sense of performance. If we interpret, however, the first part as not doing your homework gets you bad grades, then this fallacy becomes the fallacy of negating the antecedent.
4. One could say that the entrepreneur has vested interest in people donating money to his non-profit organization and thus what he said is false.
5. The fact that Mary arrived late is bad might mean many things. Perhaps she has school tomorrow or just making a bad habit. Maybe she does finishes her dinner first.

New/Old 'Fallacy': "Nonsense" a declaration of a difference without a distinction. Depending who, when, where, and how such a statement is being heard it may not fulfill #3 criteria of a Logical Fallacy. That is, the average person may not be deceived by such nonsense.

Why wouldn't this be considered an extreme application of the either-or fallacy? Or as
Dr. Bo categorizes them under Affirming a disjunct:

"(also known as: the fallacy of the alternative disjunct, false exclusionary disjunct, affirming one disjunct, the fallacy of the alternative syllogism, asserting an alternative, improper disjunctive syllogism, fallacy of the disjunctive syllogism)

New Terminology:

Disjunction: A proposition of the "either/or" form, which is true if one or both of its propositional components is true; otherwise, it is false.

Disjunct: One of the propositional components of a disjunction.

Description: Making the false assumption that when presented with an either/or possibility, that if one of the options is true that the other one must be false. This is when the “or” is not explicitly defined as being exclusive.

This fallacy is similar to the unwarranted contrast fallacy.

Logical Forms:

P or Q.

P.

Therefore, not Q.



P or Q.

Q.

Therefore, not P.

Example #1:

I can’t stop eating these chocolates. I really love chocolate, or I seriously lack willpower. I know I really love chocolate; therefore, I cannot lack willpower.

Explanation: Ignoring the possible false dilemma, the fact that one really loves chocolate does not automatically exclude the other possibility of lacking willpower.

Example #2:

I am going to bed or watching TV. I am exhausted, so I will go to bed; therefore, I cannot watch TV.

Explanation: It is logically and physically possible to go to bed and watch TV at the same time, I know that for a fact as I do it just about every night. The “or” does not logically exclude the option that is not chosen.

Exception: If the choices are mutually exclusive (either by necessity or indicated by the word "either"), then it can be deduced that the other choice must be false. Again, we are working under the assumption that one of the choices we are given represents the truth.

Today is either Monday or Sunday. It is Monday. Therefore, it is not Sunday.

In formal logic, the above is referred to as a valid disjunctive syllogism.

References:

Kilgore, W. J. (1979). An introductory logic. Holt, Rinehart and Winston.

To me, it suggests a false dichotomy, even if it doesn't explicitly present the two as the only options. It also assumes that the two are actually opposites, which might not be true even if they really were the only options,