The fallacy you’re describing is usually the straw man fallacy.

What’s Happening In That Situation?

When someone attacks your position after omitting key parts of your argument , they are typically:

  • Distorting or oversimplifying what you actually said
  • Ignoring important qualifiers, context, or evidence you included
  • Then “refuting” that weaker, distorted version instead of your real view

That is exactly what defines a straw man: misrepresenting an opponent’s argument to make it easier to knock down.

Related Fallacies That Are Close

There are a couple of closely related ideas worth knowing:

  • Cherry picking / suppressed evidence : Selecting only those parts of what you said (or the data) that help their case while silently leaving out what hurts it.
  • Quoting out of context : Lifting a piece of your argument from its context so that it seems to mean something different or weaker than you intended.

When the omission of key parts leads to a changed or weakened version of your position that they then attack, it is best classified as a straw man fallacy.

Quick Forum-Style Takeaway

If someone “forgets” your strongest points, trims your nuance, and then argues against that trimmed-down version, they aren’t beating your argument — they’re attacking a straw man.

TL;DR: Attacking your position by leaving out crucial parts of your argument is typically a straw man fallacy, often achieved through selective omission (cherry picking) or quoting out of context.