One way of testing whether something is objective is whether the law of noncontradiction applies to it. For example, if I say "The cat is on the mat" and you say "the cat is not on the mat:, once we figure out which cat and which mat, only one of us can be right, and the other has to be wrong. However if I say "McDonalds has better burgers than BK," and you say "No, BK's are better," we haven't really contradicted one another, because each is making truthful claims aboout our own taste buds. We can't apply the law of non-contradiction.
"Abortion is always wrong, except in cases where the mother's life is in danger."
If one person asserts that, and the other denies it, does one person have to be wrong? Can we apply the law of non-contradicion?