The
relativist fallacy, also known as the
subjectivist fallacy, is claiming that something is true for one person but not true for someone else. The fallacy is supposed to rest on the
law of noncontradiction. The fallacy applies only to objective facts, or what are alleged to be objective facts, rather than to facts about personal tastes or subjective experiences, and only to facts regarded in the same sense and at the same time. On this formulation, the very name "relativist fallacy"
begs the question against anyone who earnestly (however mistakenly or not) holds that there are no "objective facts." So some more work must be done, in a non-question-begging way, to make it clear wherein, exactly, the fallacy lies.