people understandably love to understand complex things as simple logical puzzle pieces. they do it with words too. people have this tendency to act like words are formally-defined mathematical concepts, and then agonise over whether their experiences fit those concepts, then use those concepts as proof for their arguments. this is, of course, essentially simply a description of communicating with language, and for most words it's absolutely fine; the words have so little variance and breadth in definition that it doesn't matter. the issue arises when the words are not clearly defined, and it becomes even worse (and more common) when the words are emotionally loaded. people adore using emotionally, loaded, weakly defined terms to end an argument quickly. it's essentially sophistry. we're all absolutely awash with these terms right now due to the dominance of headlines, tweets, content titles and other short form stretches that demand dense, emotionally charged meaning in a small space. if you'd like some examples, take "fascism", "sexual harassment" and "eugenics".

don't say someone is "essentially a eugenicist". it's such a vaguely defined term that this borders on useless. if you believe something like this, justify it with: "she supported x policy I disagree with" or "she believed in the reduction of y trait in the populace" or whatever it is that triggered you to take on this belief in the first place