This is a tounge-in-cheek illustration of formal logic used refute the claim that high performers are never laid off, using that claim itself (made by an executive) as evidence that judgements are sometimes made without context.
In reality, there is no need to prove such an obvious point because by definition layoffs are not "for cause" terminations, the company has no legal responsibility to justify them as related to the impacted individuals.
The proof proceeds by first assuming P1 and showing that it leads to contradiction.