They said [to themselves], What shall we do? If we tell him to have her executed, tomorrow he will demand her from us when the effects of the wine wear off. If we tell him to ignore her, there is a disregard for the kingship. So they said to him, "From the day that the Temple was destroyed, and we were exiled from our land, counsel has been taken from us, and we can no longer judge capital crimes. Go to Ammon and Moav, who are dwelling in their place like wine upon sediment."
In case someone is going to say that Chazal were not telling the truth and were just said this to avoid being put in a tight spot, but that it's not really true, the Gemara continues to confirm that they were speaking the truth:
And what they said is reasonable (Rashi - it was well said and certainly true that Ammon and Moav had more settled minds), as it is written, "Moav has been at peace since his youth, and in tranquility upon his sediment; he has not been poured from vessel to vessel, and has not gone into exile; therefore, his taste stands in him, and his scent has not changed."
This is remarkable! Chazal are attesting that, due to the tribulations of exile, rabbinic judges and scholars lack peace of mind, and are less capable of judging serious matters than their non-Jewish counterparts! Can you imagine anyone saying such a thing today? They'd be slifkinned alive!
Like R. Yehudah HaNasi's acknowledgment in Pesachim 94b of the superiority of the non-Jewish scholar's views, we see that Chazal did not suffer from the "siege mentality" of Jews today. They did not see any reason to automatically deny the possibility of non-Jews possessing certain wisdom that they lacked - even in matters relating to moral and legal judgment, let alone science.
The gulf that separates Chazal from later generations is truly remarkable.