Ok so I already know the difference betweem yayin stam (wine touched by gentiles; forbidden rabbinically out of a concern for being yayin nesech) and nesech (wine used for idol worship; forbidden Biblically).
However, could you say that the rabbis never feared yayin nesech regarding monotheistic gentiles such as Muslims, in which case even if they made actual libations using the wine as part of a religious ritual, it would still be permitted because they are halachically monotheistic -- and therefore they never would have made a decree of stam yeinam for monotheistic gentiles?