The guy I replied to said it's always better to buff under performing weapons than nerf OP weapons. I employed a line of logic called a "logical extreme" where I devise an extreme scenario that both follows the original logic and is also an untenable position, thus showing that the original logic does not hold up and therefore shouldn't intrinsically apply to the realistic scenario.

Because in both my extreme and the real scenario, you have a weapon that was so good it made most other weapons not worth using and made the game easier than intended. In that scenario you could either go and buff almost every other weapon in the game and then make sweeping enemy balance changers to make them harder in the face of all the buffs, or you can simply nerf the one OP weapon. And I think the more sensible option is clear.