General terms:
* Counterargument: This is the most straightforward term, simply meaning an argument against another argument. It doesn't necessarily imply an extreme case.
* Rebuttal: Similar to counterargument, but often implies a more direct and forceful response.
* Refutation: This term is stronger, implying a complete disproving of the original argument.
Terms emphasizing the extreme nature of the opposing view:
* Antithesis: This refers to a direct opposite or contrast, often used in a philosophical or literary context.
* Polar opposite: This emphasizes the extreme difference in viewpoints.
* Counter-extremity: This explicitly highlights the opposing extreme position.
Terms emphasizing the invalidity of the extreme case:
* Disproof: This directly states the proving wrong of a statement or theory.
* Falsification: This refers to the process of finding evidence that contradicts a hypothesis.
* Invalidation: This directly states the act of making something invalid or untrue.
More specific terms:
* Moderate position: This implies a viewpoint that sits between two extremes.
* Balanced perspective: This emphasizes a view that considers both sides of an issue.
* Pragmatic approach: This highlights a solution-oriented approach that avoids extremes.
The best word to use will depend on the specific context and the specific arguments involved.