I am having trouble parsing/understanding/translating a sentence in the last section of the fable "the mice and the cat" (鼠と猫の事) from the 仮名草子 伊曾保物語 (Aesop's fables). Here is the paragraph in question; it's the "moral" of the fable:
Specifically it is the second sentence I don't understand:
愚か (おろか) usually means something like 馬鹿, i.e. stupid, foolish, but I think here 愚にして means the same as おろそかにする, i.e. neglect a thing or slight a person (treat them less well than one should).
ぬか|れ|たる is the 未然形 of 抜く (overtake, outdo) + れ, the 連用形 of (ら)る + the 連体形 of たり.
Here the 連体形 nominalizes the whole phrase, and たり is like った or ている in modern Japanese, i.e. it means the completion of an action or the state resulting from the completion of an action.
(ら)る is similar to (ら)れる in modern japanese. It can express passive, potential or it can be a honorific polite verb suffix. Honorific doesn't make sense here I think, and potential is ruled out by the fact that in literary style Japanese (ら)る only has potential meaning when followed by a negative (e.g. ず). So only passive makes sense, in this case 他人 would be the agent.
...にしくはなし is like ...に及ぶものはない in modern Japanese, i.e. "there is nothing that comes close to ...", "it is best to ..."
The Iwanami edition supplies the note "だまされている方がよいのだ" ("it is better to be tricked") for [the last part of?] the sentence.
So putting this together I could guess at something like:
"Now, rather than slight people [treat them with neglect] it is better [best] to be outdone [tricked] by others."
i.e. it is better to treat other people well and risk being tricked by them, that to treat them badly (and lose their trust, like the cat the fable).
But I am very unsure if this is correct or even makes sense. Effectively I am treating the sentence as a comparative construction where 愚にして is the thing being compared with.
What is the correct way to parse/translate this sentence?
FWIW, my translations of the preceding and following sentences are 其如一度人をこらす人はいつも悪人ぞと人是を疎ず。 "When somebody once causes harm to a person as in this case [like the cat in the fable], people will always think he is a villain and shun him." and かまひて末のよに人をぬかんと思はじ "One should never think that one will outdo others in the long run."