http://revach.net/article.php?id=4667

Section: Moadim   Category: The 3 Weeks
Bar Kamtza Nicks Us In the Mouth And Eye
When the King sent a Korban with Bar Kamtza as a test to prove their loyalty, Bar Kamtza secretly made a blemish in it so that they would not offer it on the Mizbei’ach, and his plan of destroying the Jews would come to fruition.  The gemara says that this Moom was either on the lip or in the eye, in a place that Bnei Yisroel consider a moom while the Nochrim do not.  Why is that?

The Be’er Mayim Chaim says in Parshas Korach that these blemishes symbolize aveiros of not guarding our mouths and not guarding our eyes, which a Jew must be very careful.  This is why the gemara says that to a Jew a mouth or eye that has been compromised with things that are forbidden is considered blemished and not fit to serve the King with.   However to a Nochri these things are trivial and they do not even consider it an aveira relative to the more stringent things that they struggle with.  Therefore a blemished eye or mouth is more than worthy in their eyes to offer to Hashem.