Just remembered this - was told it by a Jewish friend in Manchester a lifetime ago

A Japanese man applies to become a Rabbi - after much debate he was given a chance - He passed the exams with flying colours and was given a congregation to minister to
After a time he received a summons from the head Rabbi - he attended and was told:
"Look- we're all very impressed that someone from your background should take up our faith and do so well, with one exception - your circumcisions - this "Ah so" (with chopping gesture) simply isn't going down well with the parents"
Jim