I have been asked to address what is wrong with blackmail, referencing the article What's Wrong with Blackmail?" by Julia Galef.
Actually, Galef does a good job taking the first steps in an evaluation based on desirism. On this issue, I would like to note that desirism is actually supposed to explain and predict how people actually make moral judgments. In part, it is supposed to be a theory that explains our moral practices. Consequently, it is not necessary to "convert" people to desirism in order to get them to use it - only to get them to use it more efficiently. It describes what they are already doing, for the most part - their practices of praise, blame, condemnation, excuses, apologies, "ought" implies "can", non-obligatory permissions, permissions and consent, and the like.
As desirism recommends, Galef notes two different types of cases - one in which the information will cause personal harm, and one in which the public should be told.
In the first case, the blackmailer shows no concern for the victims of the person being blackmailed. In the latter case, the blackmailer shows a willingness do harm others to gain a personal advantage.
Interestingly, the source of that heinousness seems to be utterly different for different kinds of blackmail. For example, if Bob’s secret isn't hurting anyone else, but is merely a personal detail whose revelation would embarrass him, then it’s straightforward to explain the heinousness of Sue's blackmail. In these cases (for example, a past lover blackmailing Bob over details of their sex life), the heinousness comes from harming a person who’s done nothing wrong.
But what if the information pertains to a crime Bob himself is committing? For example, let’s say Bob is a CEO who is stealing from his company. In that case, most people would argue that Sue has a moral obligation to report Bob’s secret. In blackmailing Bob, Sue is threatening to do something – report the secret – that is not only legal, but moral! So whence the heinousness? In these cases, blackmail seems reprehensible not because it wrongs Bob himself, the ostensible “victim” of the blackmail, but because it wrongs the third party whom Bob’s secret crime is harming; the company’s shareholders, for example, or society as a whole. Sue’s blackmail is heinous, therefore, because she is choosing her own monetary gain over justice for Bob’s victims.
However, Galef does not seem to know where to go from here. She notes that we have a particular emotional reaction to these two types of conditions. However, this "visceral reaction" itself seems to be a poor justification for punishment. Consequently, Galef retreats and tries to ho down a different road - a utilitarian road.
Her unease over a justification that stops with a "visceral reaction" is sensible. Ultimately, this type of morality takes the form, "You disgust me; therefore, you deserve to die." However, Galef did not seem to realize that she had not reached the end of the story. We can look at our emotional reactions - our aversions to certain states of affairs - and continue to ask whether there are reasons to have them or not to have them. It is not merely the fact that we have this type of reaction, but we have many and strong reasons to have - and to promote - this type of reaction. Furthermore, we have the tools for doing so, and those tools include praise and condemnation.
People have many and strong reason to promote an interest in making people aware of those who would do harm. If the person being blackmailed is such a person, our reaction is informed in part by the fear that we or those we care about can become the victim of such a person. To prevent those harms, we have reason to promote in others an interest in exposing those who would do harm. And others have reason to promote in us an interest in identifying those people. We have tools for doing this. The tool of condemnation would be applicable to those who would be willing to help shield these types of people so long as they get a personal benefit from hiding the information. The person who would blackmail the perpetrator of a crime that has victims is not acting the way that a person with good desires would act, and we have reason to guide people away from becoming that type of person.
People also have many and strong reasons to avoid be surrounded by people who have little or no aversion to doing harm when it benefits them. The lack of compassion demonstrated by somebody who will take money to prevent revealing personal but embarrassing information indicates a lack of compassion and sympathy that is a threat not only to this one victim, but to all of us. We have reason to promote a higher level of compassion and sympathy in people around us, and they have reason to promote compassion and sympathy in us. Consequently, we all have reason to condemn this type of blackmailer - to bring our tools of condemnation and punishment against those who would engage in such actions.
This argument tells us not only why we evaluate blackmail as a moral crime, but why we respond to it with condemnation and punishment. Note that punishment is not just the cost of doing business. It is supposed to send a message - the message that we look upon such people with so much contempt that the normal inhibitions against doing harm (punishing) are overridden. (Though arguments remain for judicial due process to make sure that our condempt is directed towards those who are actually guilty.)
It is also important to note that this "visceral reaction" is not justified by supernatural forces - no divine power or intrinsic values or categorical imperatives. Nor is it self-justifying. Contrary to the subjectivist view, the mere fact that one has such a reaction does not imply that one should have that type of reaction or that the actions one has a reaction to are wrong by that fact alone. The reaction itself is subject to justification according to its relationship to other real-world natural properties - other desires.
In short, Julia Galef provided a good start towards a response according to the principles of desirism. However, she focused too much on the act and our "visceral reaction" to it, and gave little attention to asking whether the "visceral reaction" can itself be justified by its use in promoting desires that people generally have many and strong (desire-based) reason to promote and inhibiting desires that people geneally have many and strong (desire-based) reasons to inhibit.