"There is no objective right or wrong. Morality is just a matter of opinion."
This is an obnoxious moral position generally used by individuals who want their own sentiments -- their own likes or dislikes -- to determine how they are going to treat others. Such a person is simply reporting his sentiments as he would report his height or age. He then tacks on, without any justification, that merely having this sentiment is justification enough for acting on it. Nothing else is needed to make his act right but his own belief in his own virtue.
Here, there is no room for debate. If somebody reports, “I am 35 years old," we would not think to debate him with the intention of convincing him to be some other age. Yet, when a person says, “I think homosexual relationships are wrong,” or any similar moral claim, we think it makes perfectly good sense to challenge him.
Regardless of what position an individual may take on the issue, the idea that moral sentiments are something that we can debate – in ways that age is not something to debate – suggests that moral claims are not merely reports of one’s personal sentiments. There is something else there for us to discuss.
Let us take a moral sentiment as something more like weight than age.
Somebody can assert a brute weight fact (e.g., “I weigh 350 pounds") just as they can report a brute age fact (e.g., “I am 35 years old”). However with weight, we know that changing our behavior can affect our weight. In addition to the brute fact of one’s present weight, we can sensibly discuss, “How much should I weigh?” It is still meaningful to say, "You should lose some weight" in ways in which it is not meaningful to say "You should lose some years.”
The only thing we introduce with weight that makes this discussion possible is the fact that weight can be changed in ways that age cannot. In order to treat moral sentiments like weight, and not like age, we only need to discover ways in which moral sentiments can be changed.
Of course moral sentiments can be changed. The ways in which people in different cultures, and even different people in the same culture, have different moral sentiments suggest that there are things we can do to alter moral sentiments.
The most powerful sentiment-changing tools appear to be praise, condemnation, reward, and punishment. Particularly when used on children, praise and reward tend to strengthen a moral sentiment in favor of some action, while condemnation and punishment tend to strengthen aversions to some action.
Because we have the power to change moral sentiments, we can now ask, “Should we?” And we can ask, “What should we change them to?”
In order to answer this question, we get into long, noisy debates. These debates are not about how actions stand in relation to our sentiments. There is no more reason to debate this than there is to debating our age or height or our weight at a given time. These debates are about which sentiments we should have.
How are we going to employ these tools of praise, condemnation, reward, and punishment?
The person who takes moral claims to be nothing more than a report of one’s current sentiments is simply missing the point of the whole discussion. “Fine, that’s the sentiment that you have to that state right now. However, we are talking about the sentiments we are going to create with the tools of praise, condemnation, reward, and punishment. Your answer makes as little sense as the dieter who, when asked about his target weight, answers, ‘I weigh 350 pounds’.”
Please, answer the question. “The question of the wrongness of homosexuality, for example, is not a question of how it stands in relation to current sentiments. It is a question about how it stands in relation to the sentiments we should be creating with our tools of praise, condemnation, reward, and punishment. If you say that we should be creating sentiments of moral contempt – not that we have these sentiments, but we should be feeding and nurturing these sentiments – be prepared to answer why. Be prepared to explain what good this contempt will do. Because, if it does no good, then why should we foster it?”
The person who says that morality is simply a matter of opinion simply does not yet grasp the nature of moral questions.