It's correct in some cases to say that society can show its disapproval of some evil actions only by reacting to those actions in certain ways.
Take slavery, for example. If someone says, "I'm personally opposed to enslaving people, but I think it should be legal," then we know that he doesn't really think enslaving people is all that bad. The same with abortion. It's not possible to affirm the full humanity and full personhood of the unborn child while holding that abortion should be "a choice left up to the mother and her doctor."
But sometimes people get odd and incorrect ideas in their heads about how society must signal the importance of some evil.
Take, for example, federalizing crime. There is an idea out there that is both constitutionally and morally incorrect that says that, if you really think that some crime is truly bad and truly important, you will hold that it must be punished at the federal level. Often this statement will be made by an earnest pro-lifer with abortion in mind. When someone says that kind of thing, I will point out that pretty much all heinous crimes are still (rightly and constitutionally) punished at the state level rather than at the federal level. It is not signaling a disregard for the evil of rape and torture that a rape and torture that doesn't involving crossing state lines or any of the other "triggers" for federalization (e.g., certain firearms) is a state crime and is tried and punished at the state level. It's not as though the only way to show proper moral outrage for heinous crime is to have a federal police force and to federalize all serious crimes! And in fact it would be highly imprudent to do so.
But most people who say such things about abortion haven't thought of that.
What I think they really mean is something like this: If abortion is really the murder of an unborn child, then states should be required somehow, perhaps by the Constitution, at least to have laws against abortion rather than declaring it "open season" on unborn children, Well, that gets us into all sorts of fascinating issues such as the correct interpretation of the "nor deny to any person the equal protection of the laws" clause in the 14th amendment. I have an old post on that here that I still think makes some good points about equal protection and how its jurisprudence went off the rails. Then there's the question which Robert Bork addressed long ago as to whether the framers of the 14th amendment or their audience would have regarded the unborn as "persons" for legal purposes--a point that is going to be relevant to originalists.
But if someone wants to have that discussion about constitutional protections and state laws, it would be much, much better not to say, "If we really think abortion is murder, then it should be prohibited by the national government." That just doesn't follow. The murder of most 50-year-old people is prohibited at the state rather than the federal level. It isn't a necessary form of "evil signaling" to federalize a crime.
Another kind of importance signaling, in an (admittedly) totally different area, is dragging some subject in all over the place, even where it is not obviously relevant. For example, I saw someone on Facebook launch into a long discussion of sexual abuse in Christian churches and try to tie it to the Target boycott somehow, implying that people would do better to direct their energies at opposing church sexual abuse rather than at worrying about the evils of transgender-friendly store policies.
Sexual abuse of children in churches is a very serious matter, and in no way am I downplaying it. But it has precisely zip to do with boycotting Target and with opposition to Target's transgender policy. If this isn't obvious, I can spell it out further in the comments. But for the moment I'm going to take it as obvious and note generally this tacit mistaken idea: If X is a really serious problem, then it's always relevant to bring it up and connect it with any other topic or use it to downplay the importance of some other topic that people are concerned about.
Well, no. It's not as though the seriousness of X means that X can never be a hobby horse, can never be ridden to death, can never be dragged into a discussion where it doesn't make sense, can never give rise to an apples and oranges comparison. And I'm afraid that sexual abuse of children is the kind of X that causes people to get a blind spot about this, presumably because it is such a bad thing.
How much time one spends talking about something is going to be a matter of personal taste and personal motivation. Even, perhaps, personal calling, if that is not too grand of a word. I confess to being subject to the temptation that almost everybody in the social media age is probably subject to: The temptation to tell people who are chattering about Y that they should be worrying or talking about X instead, that they need to be getting a sense of perspective, that they're making a big deal about something that isn't that big of a deal in the grand scheme of things. I do that, too. Or I feel like doing it. I suppose that's what the hashtag "firstworldproblems" is all about. "Oh, poor baby, your espresso machine isn't working? Try being a Christian refugee about to be crucified by ISIS. Sheesh."
Not that anyone is likely to think it's his personal calling to complain about his espresso machine.
But I think one should admit that the transgender agenda is a big deal in its own right and that fighting it is an important thing. It's not the cultural equivalent of a broken espresso machine. Hence, people who boycott Target have a legitimate concern. That's not to say that everybody has to boycott Target. Boycotts aren't always effective, sometimes you might legitimately need something at Target that you can't find elsewhere or that is too expensive elsewhere, etc. Boycotts are almost never morally obligatory. But it is one perfectly legit way to show that Middle America knows when Target is giving it the middle finger and that Middle America is not pleased about that.
This particular type of "importance signaling" (telling people they should be talking about X instead of Y) really results from underlying political and moral differences of opinion. And it can go in both directions. If I as a pro-lifer feel annoyed when progressives, especially progressive Christians, are agonizing over veganism but never talking about abortion, that's because I think that veganism is (frankly) ridiculous and that nobody should be agonizing about it. It's also because I think human beings are more valuable than animals, that vegans really often do have a lack of a sense of the relative importance of these matters, and that the combo of veganism and not talking about abortion is probably symptomatic of a failure to appreciate the relatively greater importance of mankind, made in the image of God, over animals.
What I tend to notice sometimes (not always) when it comes to importance signaling is that, when it is coming from the somewhat more progressive side, there is a sort of tortured attempt not to come out and say this about underlying differences of opinion. Instead of saying, "I think Christians who are somewhat more socially conservative than I am are just plain wrong in their assessment of the evil and importance of the transgender agenda," they have to say something else. Something (for example) about comparing the odds of a child's being molested at Target to his being molested in a church youth group. So it's hard to get to argue about the real underlying difference of opinion--namely, the importance or unimportance of Y. Because the attempt to do this is seen as denying the importance of X. But X and Y may be non-comparable in their importance.
It isn't always the case that a person who has a hobby horse about X really disagrees with other people about the importance of their issues. There is such a thing as a "pure" hobby horse that just gets ridden on any and all occasions. I don't want to overgeneralize. But a hobby horse can be a symptom of an underlying political difference, and it can be useful to get that out into the open.
If X is bad enough, there's a fear of appearing to downplay X by accusing someone of having a hobby horse about X. And of course there's no need to start fights all over the place. Social media is unpleasant enough without recklessly losing all your friends that way! But I do think it's important not to be so intimidated by certain concerns that we let them turn into a kind of collective hysteria. And I fear that the issue of child abuse in the church is in danger of becoming precisely that sort of hysteria-inducing issue, leading even to the loss of concepts like due process and the danger (and possibility) of bearing false witness.
Importance signaling can increase this sort of hysteria if not challenged, so just occasionally, it's not a bad idea to challenge it.