英语翻译They agreed also as to the proudest moment they had know

【‘推荐答案’翻译的肯定不对!可以这样翻译】：
“他们也承认这是最庄严的时刻,这是他们早就知道的,然而,在这一最庄严的时刻,那种内心的冲动,决不是皈依在理性和实际的基础上的,而是缘于其间诸多浪漫联想的迷惑.”

calling：在这里,应当是“内心的冲动”、“感召”的意思.

帮你分析一下好了：
一、They agreed also as to the proudest moment they had known in that calling（句子主干）
其中 （that）they had known in that calling为省略了that 的定语从句,修 the proudest moment
in that calling 作状语修饰 had known （过去完成时,说明：“知道”的行为发生于agreed之前）

1、They agreed also as to the proudest moment——“就这个最庄严的时刻而言,他们也是承认的；
2、the proudest moment they had known in that calling——在那种内心冲动的过程中或发生之时,他们就知道是“最庄严的时刻”

二、which is never embraced on rational and practical grounds, because of the glamour of its romantic associations.（which引导的定语从句,修饰 that calling）
because of “原因在于”的意思,可以翻译成“缘于（因缘于）”