If we seek a purely pragmatic solution, we should perhaps heed the advice of Orwell, 1946:
Foreign words and expressions such as cul de sac, ancien regime, deus ex machina, mutatis mutandis, status quo, gleichschaltung, weltanschauung, are used to give an air of culture and elegance. Except for the useful abbreviations i.e., e.g., and etc., there is no real need for any of the hundreds of foreign phrases now current in the English language. Bad writers, and especially scientific, political, and sociological writers, are nearly always haunted by the notion that Latin or Greek words are grander than Saxon ones, and unnecessary words like expedite, ameliorate, predict, extraneous, deracinated, clandestine, subaqueous, and hundreds of others constantly gain ground from their Anglo-Saxon numbers. [footnote: An interesting illustration of this is the way in which English flower names which were in use till very recently are being ousted by Greek ones, Snapdragon becoming antirrhinum, forget-me-not becoming myosotis, etc. It is hard to see any practical reason for this change of fashion: it is probably due to an instinctive turning away from the more homely word and a vague feeling that the Greek word is scientific.]
. . . . . . . . .
The defense of the English language . . . has nothing to do with archaism, with the salvaging of obsolete words and turns of speech, or with the setting up of a "standard English" which must never be departed from. On the contrary, it is especially concerned with the scrapping of every word or idiom which has outworn its usefulness. It has nothing to do with correct grammar and syntax, which are of no importance so long as one makes one's meaning clear, or with the avoidance of Americanisms, or with having what is called a "good prose style." On the other hand, it is not concerned with fake simplicity and the attempt to make written English colloquial. Nor does it even imply in every case preferring the Saxon word to the Latin one, though it does imply using the fewest and shortest words that will cover one's meaning. What is above all needed is to let the meaning choose the word, and not the other way around.
Of course, if fewer and shorter words are called for, Saxonate terms will often win the day over their Latinate analogs. Nevertheless, the colonial mindset which deems these words "dirty" or "obscene" may at first hamper their use in the public sphere. To combat this prejudice, we may compare not the political history of these terms, but rather their etymological history. Such a Nietzschean "genealogy" may provide us with an alternate perspective from which to compare the relevant terms without the burden of spurious (i.e. politically-inculcated, or slave mentality) moralistic bias.
Consider, for example, shit, shit and feces, defecate: if we examine their etymologies, does one emerge from a more innocent, i.e. euphemistic perspective on the intended referent than the other? [etymologies courtesy Shipley, 1984]
Although the Indo-European root of feces is unclear (perhaps *bhƒy-), its more recent history is well known:
feces, however, is from L[atin] faex, faeces: sediment, dregs. The basic sense of defecate is to clear out the dregs, cleanse, purify. Thus, Robert Burton, in The Anatomy of Melancholy (1621), states that Luther "began upon a sudden to defecate, and as another sun to drive away, those foggy mists of superstition." And fallible man is comforted by H. Macmillan in The True Vine (1870): "By the death of the body, sin is defecated."
Shit, on the other hand, can be traced back to the Indo-European sek, to cut, separate, or divide:
shite, shit, dropped from the animal; earlier skate, skite, as in blatherskite. blather: to talk nonsense loquaciously, as with verbal diarrhea. skate: shitter, originally a Scotch term of contempt, is now softened in the colloquial "He's a good skate." The Scotch song Maggie Lauder, by F. Sempill, 1650, a favorite with the American Army in the Revolution, contains the line: "Jog on your gait, ye blatherskate." Variants are bletherumskite and blatherskite. An informative Paston family letter written in 1449, relates: "I cam abord the Admirall, and bade them stryke [pull down their flag] in the Kyngys name, and they bade me skyte in the Kyngys name." (Note that sk, as still in Scandinavian tongues, was long sounded sh in English.)
Perhaps by some standards, then, shit is the more euphemistic, as it initially referenced the act of separation, not the waste itself (as with feces). Nevertheless, the much longer history of shit in English indicates it's use in literal reference to bowel-movements dates back at least to 1449, while defecate enjoyed a more general [metaphorical?] sense of removing waste at least as late as 1870. Here, again, however, it seems impossible to separate out the role of Latinate-bias in such choices, and the prospects for any objective account of relative "obscenity" seem dim.
[As should be expected given the inherently subjective nature of the language - world relationship.]