The following sentence is from Charles R. Kesler's Claremont Review of Books article, Thinking about Trump:
It is not entirely clear whether his liberal and conservative critics disapprove of Trump because he violates moral law or because he is infra dig.
The 'infra dig' threw me for a moment until I realized it was a popularization of infra dignitatem, 'beneath (one's) dignity.' According to this source, Sir Water Scott in 1825 was the first to use the abbreviation.
I was taught to italicize foreign expressions, which is precisely what the good professor did not do in the sentence quoted. Where's my red pen?
As for the content of the sentence quoted, it is clear to me that the Never Trumpers (who are of course conservatives of a sort by definition) despise Trump mainly because the man has no class and is therefore infra dignitatem. He is not one of them. He does not have the manners and breeding of a Bill Kristol or a George F. Will and the rest of the effete, yap-and-scribble, do-nothing, bow-tie brigade. He is an outsider and an interloper who threatens their privileges and perquisites. Better Hillary and the status quo than a shake-up and take-on of the Deep State and its enablers.
On the other hand, leftists, most of them anyway, don't give a damn about the moral law as it pertains to marital fidelity and sexual behavior with the possible exception of rape. These types don't object to Trump because of locker-room talk and sexual affairs. After all, they tolerate it in themselves and their heroes such as the Kennedy’s, Martin Luther King, Jr., and Bill Clinton. What they are doing is right out of Saul Alinksy's Rules for Radicals, in particular, #4: "Make the enemy live up to its own book of rules."
Nor do leftists much care that Trump is infra dig. What leftists object to are his policies and programs, but instead of addressing them, they attack the man for failing to honor values that they themselves do not accept so as to discredit him among his supporters.