When you read biographies of politicians and other public figures going back many decades, you see that crude language is by no means a recent phenomenon in the precincts of power.
What has changed dramatically in recent decades is the willingness of some news outlets to reproduce their salty language. The New Yorker is among the publications that have adopted this relatively new approach. And of course, many online-only outlets are even less circumspect about crude language than The New Yorker.
It hardly comes as a surprise these days that if political opponents start talking colorfully about one another's posteriors (or "keisters," as one politician preferred to call them), the verbatim version of the language will come out.
On the other hand, as far as I know, the Associated Press still hews to the older standards of diffidence toward coarse language. To that end, the Associated Press Stylebook (2002) lays down the following guidelines for handling such words:
obscenities, profanities, vulgarities Do not use them unless they are part of direct quotations and there is a compelling reason for them.
When a profanity, obscenity or vulgarity is used, flag the story at the top:
Eds: Note contents of 4th graf.
Then confine the offending language in quotation marks, to a separate paragraph that can be deleted easily by editors who do not want it.
In reporting profanity that normally would use the words damn or god, lowercase god and use the following forms: damn, damn it, goddamn it. Do not, however, change the offending words to euphemisms.Do not, for example, change damn it to darn it.
If a full quote that contains profanity, obscenity or vulgarity cannot be dropped but there is no compelling reason for the offensive language, replace letters of an offensive word with a hyphen.
When the subject matter of a story may be considered offensive, but the story does not contain quoted profanity, obscenities or vulgarities,flag the story at the top:
Editors: The contents may be offensive to some readers.
Regrettably, AP fails to identify which words are obscene, which profane, and which vulgar, perhaps to avoid shocking the reporters and editors who occupy a typical newsroom. It's a darned (I mean d-----) shame, really.
But to answer your questions:
In much of the United States, "ass" continues to be viewed as unacceptably vulgar language, though probably not as outright obscene in most places.
“Remain on one’s ass” is as precise an antonym for “get off one’s ass” as I can readily imagine.
"Ass-wise" (as opposed to "wise-ass") is not a word in common use in this country, but it undoubtedly means something along the lines of "with regard to, on the subject of, or in connection with asses."