Tā yǐnyòng bùyìjūnzǐhū lái zànyáng péngyǒu de qìdù.
He quoted 'is that not a gentleman' to praise his friend's composure.
Tips
history
From the opening passage of 《论语·学而》: 学而时习之，不亦说乎？有朋自远方来，不亦乐乎？人不知而不愠，不亦君子乎？ (To learn and regularly practice - is that not a joy? To have friends come from afar - is that not a pleasure? To be unrecognized yet not resentful - is that not a gentleman?). The three rhetorical 不亦...乎 questions are among the most famous lines in all of Chinese literature, often memorized by schoolchildren.
usage
不亦...乎 is a classical rhetorical pattern ('is it not...?'). 说 in the opening 不亦说乎 reads yuè (= 悦, 'joyful'), not shuō. The third question 不亦君子乎 is the moral climax.
