Avnei Nezer on When We Can Treat Jews Like Non-Jews (2 Sivan)

שו"ת אבני נזר יורה דעה קכ"ו 2 Sivan 5656 (1896)

A Jew wants to buy non-kosher cuts of meat, whether from kosher animals or not. Now that the local Jewish meat-sellers have caught wind of the fact that he's Jewish, they don't know what to do. Do we treat a Jew who has abandoned observance as a Jew, which means we cannot be part of his/her sins, or as a non-Jew?