On the other hand, if someone adopts a simple relativist stance as an ad hoc defense of a controversial or otherwise compromised position—saying, in effect, that "what is true for you is not necessarily true for me," and thereby attempting to avoid having to mount any further defense of the position—one might be said to have committed a fallacy.
The accusation of having committed a fallacy might rest on either of two grounds: (1) the relativism on which the bogus defense rests is so simple and meritless that it straightforwardly contradicts the law of noncontradiction; or (2) the defense (and thus the fallacy itself) is an example of ad hoc reasoning.
One may introduce arguments for and against this proposition, based upon such things as standards of statistical analysis, the definition of "overweight," etc.
Conversely, take the new statement by Alice, who is 5 feet 6 inches (1.68 m) tall, "270 pounds (120 kg) is grossly overweight."
As he is discussing something that is true about himself, he is not barred from making an argument that considers subjective facts, and so he does not commit the fallacy.