Personally you may believe that their opinion is not valid but under the system of subjective morality, you have to acknowledge that their opinion is just as valid as yours and has a right to stand as it is just another subjective opinion under that system.
Morality is based on philosophical beliefs that are not measured directly by science so this is a different form of evidence-based which is based on propositions. But if you want the type of evidence that you claim by science then the only way is through indirect evidence which comes from lived moral experience.
Then why do most people IE
Most of us see ourselves as capable of recognizing what is good, bad, valuable, and worthwhile. We think of ourselves as beings whose moral beliefs — about the badness of suffering, for example — are objectively true.
https://arcdigital.media/morals-are-objective-d647dc5bf12a
People are often unwilling to think of ethics as their own preferences, rather than demands from something more transcendent. For instance, it’s normal to claim that one really wants to make one choice, but it’s only ethical to make the other.
Morality is subjective preference, but it can be objectively wrong
including the experts say that our lived experience shows there are objective morals. IE
Are there good arguments for objective morality? What do philosophers think about moral realism?
A 2009 PhilPapers survey shows that 56.4% of philosophers were moral realists, 27.7% weren’t, and 15.9% held some other position. For every philosopher who thinks there aren’t any objective moral facts, two philosophers think there are.
But even philosophers who are committed to moral anti-realism think that there are some good reasons to be a moral realist. They don’t think that proponents of objective morality are just confused, rhetorically sneaky, or crypto-theists.
But if the question was not “is moral realism true” but “is there a good case to be made for moral realism”, I suspect the percentage would jump from 56.4% to somewhere in the high nineties.
Are there good arguments for objective morality? What do philosophers think about moral realism? : AskPhilosophyFAQ
So just about all the experts in the field of ethics and morality, the ones who understand and know best about morality think there is a good case for morals being objective.
I don't get your argument, it is a strange logic. You earlier were using animals as having similar morals to humans. I was saying that if morality was created by evolution, the need to survive then just like the lion killing another lion and their cubs would be OK to do if it meant survival. In other words, evolution does not explain the moral right and wrong.
Please refer to the above link I have posted. Actually it seems you link lend more support for what I am saying. IE
Moral relativism is an important topic in metaethics. It is also widely discussed outside philosophy (for example, by political and religious leaders), and it is controversial among philosophers and nonphilosophers alike. This is perhaps not surprising in view of recent evidence that people's intuitions about moral relativism vary widely. Though many philosophers are quite critical of moral relativism, there are several contemporary philosophers who defend forms of it.
Your link seems to say that moral relativism is a controversial topic among philosophers. That many philosophers are critical of moral relativism and only several philosophers defend it. This supports my link that the majority of philosophers support moral realism. Just a footnote moral relativism though similar to subjective morality is a little different in that moral relativity usually applies to cultures having different moral views to their relative position.
OK then I have to point out again that
If the measurement point for moral right and wrong is within humans then whatever and whoever can make a good argument for what is right and wrong will be the measure of what is right and wrong. That could be almost anything and we have seen this in society. IE a moral wrong can be argued as right and there is no way to independently measure it is truthfully bad.
My point is is that a subjective moral system cannot determine what is ultimately right or wrong morally and therefore what you consider a moral wrong can be justified as being OK to do. You have to accept that is part of the system. Whereas under an objective system I can say no that claim that the act is a valid subjective view is objectively wrong no matter what the person argues or claims.
A subjective moral system has no real authority to weed out what we would consider always wrong because there is no way to tell. Your personal opinion is not enough as the person claiming the moral position you think is horrible can claim that this is my personal view and I have just as much right as you to hold that.
So what about those in other countries who believe that a woman should not have the same status as a male today. Do they have a right to hold that view under a subjective moral system?
The problem you have with trying to make moral meaning out of a subjective system is that because it always changes and allows relative and subjective positions it has to allow all those different positions whether 100 or 10 years ago or now or whether in one country or culture or another. It all doesn't matter because morals are subjective and relative and all views count. None or more right than others.
You can personally say they are wrong but under the system of subjective morality, you cannot say that differing views you may find evil are wrong. Because people who hold those evil views don't think they are evil but in fact are OK. So who is truthfully right or wrong, who knowns as there is no independent measure outside personal opinions that can inform anyone.