A quote from Esser Agaroth:
Yehoshu’a ben Perahiyah and Nittai the Arbelli received it [the Torah] from them. Yehoshu’a ben Perahiyah says make for yourself a rav, acquire for yourself a friend; and judge each Jew favorably. (Mishah Avoth 1:6)
As politically-incorrect as it may be, the Ramba”m, and others teach that the word אדם/adam indicates “Jew” in this mishnah. R’ Ovadiah meBartenura goes a step further, and says this refers to a “kosher Jew,” those who believe in the Torah, and observe it.