A general form of argument I've seen a number of times in the past year: The difference between my opponent and myself is that whereas my opponent is concerned with (some practical thing, like consolation, charity, fairness, etc.), I'm interested in the truth. This appeal to truth is incantatory: it is not an argument but a rhetorical ploy that usually involves a false dichotomy. By ritually displaying one's 'interest in the truth' in contrast with someone else's interest in something else, one simultaneously paints oneself as in possession of the truth and the other person as compromising the truth in favor of something else; when, of course, it is entirely possible that their concern with whatever it may be is itself a form of interest in the truth. Certainly, nothing says that you can't simultaneously be interested in the truth and interested in other good things as well; and there is no reason to think that truth excludes every other good thing there may be.
It is also ironic, in that someone who appeals to truth this way is usually showing that they do, in fact, have other interests; one of which is to be superior to their opponents when it comes to the reputation for the truth. There are no doubt innocent uses of the argument. But usually you can almost guarantee that the person who uses it is merely posturing to win an argument; they may be generally interested in truth, but they are gunning for a victory
Except in rare cases we can assume that everyone is interested in the truth. But interests in truth pave the road to irrationality in much the same way good intentions pave the road to hell. Indeed, wanting to do good and wanting to find truth are closely related; and the same thing can be said of both. Interest in the truth is pointless without the rightly ordered pursuit of truth. That is not a formula you say but a way you go about things, and the fundamental irrationality in arguments like the above is that someone acts as if you could show that you pursue truth well by saying you pursue it, and this is as absurd as thinking you could show that you are virtuous by insisting that you are virtuous in public. (Since the right sort of interest in truth is a virtue, it is in fact the same thing.) That way lies hypocrisy, not virtue.
There are other incantatory uses of the word 'truth'. Are any of them rational? Perhaps when they are deployed like Socrates's rhetoric -- to hold oneself to a standard and to encourage oneself to do better. But is there any other case where it would be rational?