anyone who doesn’t act like a jew, (i.e. believes the 13 ikkarim and keeps shabbos publicly) one is obligated to hate with utmost contempt, in your heart and externally. this has nothing to do with knowing what is in someone’s heart. this is the clear psak of the chofetz chaim. no issur of lashon hara, rather one is obligated to dan l’kaf chov and speak badly on them. there is no din aravus, there is no issur of ribis, they have a din of a goy.
this is the din of a heretic regardless of them also having the din of a “tinok sh’nishba”. Such a person does not have a portion in the next world.
there is still an obligation of basic chesed to such a heretic, and a lot of the dinim l’maaseh are questioned for various reasons by gedolai poskim. so, we are generally accustomed to take the chumra both ways, maybe they have the “din of a yid” maybe “din of a goy”. However, the hatred towards anyone who acts like a goy is deeply important. Such a person is not part of “klal yisroel”.