Translation of phrase 「留守を預かる者として、主の家を汚した蒙昧」

Could somebody help me with translation of the following sentence.

留守を預かる者として、主の家を汚した蒙昧――八つ裂きにされようと文句は言えぬ。

Text:

理屈など通用しない。 ただ一人でも、どんなに卑小な者だろうと、名誉と忠誠に反した愚者を、黒円卓に存在させた罪は罪。 故に罰。 留守を預かる者として、主の家を汚した蒙昧――八つ裂きにされようと文句は言えぬ。

Some sort of translation:

An ignorance of staining master's house, as a person taking a charge of it during his absence --

Context: The master of a some sort of group is not present for some long period of time, so he entrusted the control of the group to his subordinates. However one of them done something bad, so the master is punishing all of his subordinates.

Answer

I tried my hand at a free translation, because I couldn't figure out how to translate it preserving the meaning or sentence structure precisely:

Utter nonsense. The crime of allowing even one fool who has gone against honor and loyalty at the black round table, no matter how low they might be, is nonetheless a crime. And so, there must be punishment. Such foolishness, to have defiled your lord's house so while it was left in your care―it would be only just were you rent limb from limb.

Unfortunately, this doesn't match up perfectly with the original. I'll try to comment on your translation and the original sentence:

留守を預かる者として
as a person taking a charge of it during his absence

You seem to understand the literal meaning of this part fairly well. But the master entrusted it to an entire group, right? So it's "people" rather than "a person". For people who were left in charge of the master's house while the master was gone . . .

主の家を汚した蒙昧
An ignorance of staining master's house

My comments:

1. 
   

   In this case, I think 汚した is figurative (as it often is), so I chose to translate it with "defile" instead. Their crime of allowing even one such person, no matter how low their station, to be at the black round table has defiled their master's house, and so they must be punished.

   
   


2. 
   

   Translating 蒙昧 is hard, and I had to rely on dictionaries to figure this out. I think it's figurative, literary language, in which the metaphor is light as knowledge or intellect, and darkness as the lack thereof. The word 蒙昧 represents that lack, and I've chosen to translate it as "foolishness".

   
   


3. 
   

   I don't think "An ignorance of" really makes sense or captures the relationship between 蒙昧 and the rest of the sentence. I think that grammatically the entire clause is a gapless relative that modifies the following head noun 蒙昧. Basically, 蒙昧 "sums up" the clause. (I think it's what Martin calls a "summational epitheme" in his Reference Grammar of Japanese.)

   
   

   That is, for people who were left in charge, defiling the lord's house (with their crime) was utter foolishness.

   
   
   

This text, by the way, uses a rhetorical device called 体言止め several times. It adds force to the original by ending on a noun (e.g. 罪 or 罰). In this sentence, the last word is 蒙昧, but it's followed by a long dash, after which the speaker elaborates with another sentence, "It would be only just (or literally 'You could not complain if') you were torn limb from limb", which is a comment on that foolishness.

So basically, the lord/master guy is pretty cheesed off.