I just explained it in my post. If Jesus came down to Earth tomorrow, and made some morally atrocious statement, would that make it right? If Jesus said "rape and kill, do whatever you want, it's all cool, so long as you enjoy yourself" would you start raping and killing? I think not. If he said "Segregation is good, I don't like those dark-skinned people" would that make racism holy? If Jesus opened his own abortion clinic, would that make infanticide a sacrament? Of course not!
And what if someone has different ideas about what's right and wrong than you do?
Nobody (at least nobody I know of) has a perfect view of the world. Nobody has direct access to the truth. We make do with the best we can. If someone disagrees with me about an issue, there are some things to take into account: are they mentally sharp, are they philosophizing in good will, and are they looking at the same information as I am? Those are all worth taking into account, so we can try to work things out. But we never will all agree on all the issues, that's okay. We don't have direct access to morality, we don't know for certain exactly what is right or wrong, but we can do a pretty good job of figuring it out if we try.