And the uncleanness of a corpse is never attributed to a people as a whole, only uncleanness that is the opposite of holiness or uncleanness of a consecrated object. For instance, the Torah will say that idol worshippers defile sacred property and the Temple, making them unclean. And whenever the Scripture talks about topics which attribute uncleanness to a people as a whole, they will only come with respect to idol worship, immorality, and murder.

And the language זנות (immorality) which comes with respect to a people as a whole always comes with respect to the idol worship.