פירוש על עבודה זרה 52:10

In a case where the circumcision can be done only by a non-Jew or a Samaritan (a group similar to the Jews, but with a different center of worship), R. Meir says that the non-Jew should circumcise and not the Samaritan. This is probably because the Samaritan has the wrong intent, whereas the non-Jew has no intent. R. Judah allows the Samaritan but not the non-Jew, probably because the Samaritan is in some ways a Jew. In any case, this proves that R. Meir does allow a non-Jew to circumcise a Jew.