The prohibition is based on Leviticus 19:16, in the context of regulations about relations between people [verses16-18]. In this chapter, the phrase "the congregation of the children of Israel" is used several times. In Exodus 16 and 17 this phrase is used when people were complaining. In Exodus 35 in connection with the bringing of contributions for the Tabernacle; in Leviticus 16 – with respect to atonement; in Numbers 1 with regard to the physical arrangement of the Israelite camp in the wilderness; in chapter 8 – the separation of the Levite tribe from the rest of the children of Israel; in chapters 13 and 14 in connection with the sin of the spies, and those who followed them; in chapter 15 with respect to atonement [according to halachic tradition – for Idolatry]. From the context: verse 3 "and keep my Sabbaths" it seems clear that this is not meant to apply to non-Jews. So it does not appear to be directed to non-Jews. This prohibiton is NOT in the list of sixty-six commandments of Bnei Noah compiled by the contemporary Rabbi A. Lichtenstein.
The fact that verses 16, 17 and 18 uses the words "among thy people", "thy neighbourneighbor", "thy brother", "children of thy people" it is clear that Noahides are not subject to these commandementscommandments.
However, we see that the Torah views the various types of ill-talk about members of one's community as having a bad result to the community. Thus it seems it would be wise that Noahide communities adapt them – for the benefit of the community.
