Professional philosophers continue to make unsubstantiated claims about human psychology without presenting any empirical evidence to support their claims. It's really bizarre. See this remark from Nathan Nobis. There is no good evidence that most people think any of the things he says, and even if they did, every single one of these thoughts is consistent with antirealism.

More importantly, there is empirical evidence to the contrary. Here is my response to Nathan:

Hi Nathan. I’m consistently frustrated when philosophers make claims about human psychology without appealing to or conducting the appropriate empirical research. What most people tend to think is an empirical question best addressed using the tools of social science. To my knowledge, you're not a social scientist and have not conducted or engaged in empirical research on how nonphilosophers think about moral realism, nor have you presented or appealed to any empirical evidence to support any of your claims. If you want to know how nonphilosophers think you should consult appropriate research rather than relying on speculation, personal anecdote, or whatever armchair rationale analytic philosophers typically rely on.

At present, there is no compelling body of empirical evidence to support any of your claims. Worse still, they are all described in a way that would be insufficient as an operationalization of an indication of support for moral realism.

“(1) moral mistakes are possible: "I used to think doing X was wrong, but I was mistaken about that”

A belief in the possibility of moral mistakes is consistent with many forms of moral antirealism, so this would not be especially diagnostic of people being moral realists. There’s also no compelling body of evidence showing most people think moral mistakes are possible. “Mistake” would also have to be operationalized. For instance, a relativist could believe it’s wrong to steal, and steal anyway, acting against their own moral standards. Presumably they’d think they were making a moral mistake. But that’s different then being mistaken about whether or not stealing is morally right or wrong in the first place. It’d be challenging to conduct research on this, and I don’t know of any such research. Even if there is some, there won’t be much. There’s no robust cross-cultural body of data showing people think moral mistakes of the relevant kind are possible.

“(2) that collective mistakes are possible--there's moral progress and decline, not just change”

First, progress and decline is consistent with many forms of antirealism. It’s even consistent with relativism: there is progress or decline relative to the moral standard in question. The concepts of progress and decline do not require, presuppose, or even hint at realism. People make progress on personal goals, or at becoming better artists, for instance. People can and do already employ the notion of progress and decline relative to self-chosen goals all the time.

Second, there is no established body of empirical evidence that supports the claim that most people think moral progress in such a way that is most consistent with realism is possible. On the contrary, the best available study that specifically addresses the question of objective moral progress suggests most people reject this idea. Here is an excerpt from the abstract:

“Our results suggest that, neither abstractly nor concretely, people dominantly believe in the possibility of objective moral progress, knowledge and error. They attribute less objectivity to these phenomena than in the case of science and no more, or only slightly more, than in the cases of social conventions and personal preferences. This finding was obtained for a regular sample as well as for a sample of people who are particularly likely to be reflective and informed (philosophers and philosophy students). Our paper hence contributes to recent empirical challenges to the thesis that people believe in moral objectivity.”

Pölzler, T., Zijlstra, L., & Dijkstra, J. (2024). Moral progress, knowledge and error: Do people believe in moral objectivity?. Philosophical Psychology, 37(, 2073-2109.

“(3) that just because someone, or some group, disapproves of people doing some action X, that doesn't necessarily mean doing X is wrong,”

This would at best only indicate whether people endorsed agent relativism, so this would not be a good way to ensure that people are not appraiser relativists nor any other form of antirealist. As such, rejecting this notion would not be a strong indicator that a person is a moral realist. I reject this, and I’m the most prolific antirealist there is. As such, this is not diagnostic of or strongly indicative of being a moral realist. Furthermore, this once again is an empirical question and at least some studies that use wording consistent with agent relativism not only find that many participants select these response options, but that variations of relativism were the most common response even after participants underwent training in familiarizing themselves with metaethics and were given comprehension checks and detailed response options. And this held up across seven different paradigms. Does this mean most people are moral relativists? No, but it is better than anecdotes and the self-reports of philosophers. See here:

Pölzler, T., & Wright, J. C. (2020). Anti-realist pluralism: A new approach to folk metaethics. Review of Philosophy and Psychology, 11(1), 53-82.

“(4) that there can be disagreements in ethics, with one side being mistaken, and with no good reasons for their reviews”

Again,you present no evidence that most people think this. The main paradigm in experimental metaethics is, incidentally, the disagreement paradigm. And it in fact finds very high rates of antirealist responses from participants, especially in newer, better-designed studies. Furthermore, disagreement is consistent with antirealism.

In addition, there is some empirical evidence suggesting folk notions of disagreement differ from the kind that would support the notion that they are implicit realists. See:

Khoo, J., & Knobe, J. (2018). Moral disagreement and moral semantics. Noûs, 52(1), 109-143.

From the abstract: “We show that there are moral conflict cases in which people are inclined to say both (a) that the two speakers disagree and (b) that it is not the case at least one of them must be saying something incorrect.”

In short, not a single one of your four examples, even if it was true, would be good evidence that people are realists, since all such responses are consistent with antirealism. Second, whether most people think anything in particular is an empirical question and you present no empirical evidence to support your claims. At present, there is no good evidence most people are moral realists.