In Parshat Balak, it is the third time in the Torah that we are taught the idea that, "those who bless you will be blessed and those that curse you will be cursed."
This is more of a warning to the nations of the world. If they treat the Jewish people well, it will be good for them. If they don't, they will suffer severely. Even though Hashem sometimes sends the nations to punish Israel, if they are too zealous in carrying out their mission, they will suffer.
The treatment of Am Yisrael in Egypt is a case in point. Because they made us suffer in a cruel way, they were doomed to perish in the Red Sea. The Rambam points out that the Egyptians who did not want to oppress the Jews, could have refused.
On the other hand, Rav Aharon Soloveitchik זצ״ל, once said that when Gentiles show kindness towards Israel, we are to treat them kindly by not taking interest from them. Rav Soloveitchik included Evangelical Christians as an example of Gentiles showing kindness, even though they have an agenda.
This Pasuk of, "those who bless you will be blessed and those that curse you will be cursed," has great relevance even today.