I believe that there are acts such as rape and first degree murder that are objectively wrong. Now if I’m a relativist I can’t say that. All I could say is that I personally believe it is wrong, but someone could say it’s good and be justified because morality is relative.
There are a couple of points to be made here.
Do you see how you described murder? For it to be morally wrong, you had to use the term ‘first degree’. Which defines a specific set of circumstances that must be relevant to the act of killing to be able to class it as morally wrong. It has to be unlawful, it has to be intentional, it has to be premeditated and it has to be done with malice aforethought. Those are the conditions under which you can describe it as being first degree murder and, as you believe, to be described as morally wrong. That is, the act is conditional to those cicumstances. It is relative to those conditions.
Now you’d be hard pressed to find anyone except psycopaths or sadists who, given those conditions, would argue that there was nothing wrong in taking a life in that specific manner. But the act you are describing is one that is relative to the conditions (willfull, premediated etc). So saying that it is wrong is, by definition, a relative call and not objective.
The situation with rape is the same. It describes an act causing harm to another person in a specific way. Just like we have a catch all term in ‘first degree murder’ to describe the taking of a life that is morally wrong, we have a term in ‘rape’ that describes harm to a person which we desribe as being morally wrong. But both terms describe the conditions either explicity or implicitly.
Once so described, then all reasonable people would agree they are wrong. But, and this is important, even if every single person agreed it was wrong it would not make the act morally wrong in an objective way. All acts are contingent on circumstances and are therefore relative. One just needs to unpack what is being described to realise that.
Having said that, the argument seems to deny moral relativism in any way. And that by admitting to relativism, it would be impossible to claim any objective truths. That makes no sense to me and appears to be a bullwark against what might be seen as a slippery slope to accepting all things as being relative. Hence the bizarre refusal of some posters to answer simple hypotheticals which cannot be answered in any way without proving that the answer is a personal opinion relative to the conditions.
If this were a discussion in a bar, the hypothetical euthanising of the pet dog would need to be answered. It couldn’t be ignored. One couldn’t blanly stare at the wall until a different question was asked. I’d keep asking it until we had an answer. But the forum eqivalent is: ‘I’ll ignore that until the conversation moves on because any answer I gives concedes part of the argument’.