Just because there is a gradual spectrum between two states doesn't mean we can't draw distinctions. For example, just because we cannot define the exact, precise color when blue turns into green, it does not mean that blue and green are the same color for any normal person discussing an issue publicly in good faith.
When someone says "X and Y are on a spectrum, X is good and Y is bad", the point is to highlight the differences. Pointing out that the spectrum or continuum might not have a precise boundary has literally zero weight towards the validity of the ultimate conclusion a person is making here and really is just a complete derail done by people who have no substantive points to make.