Ribis is heresy

 Alshech (Devarim 23:21) you can charge interest to non-Jews This verse reveals the reason for the prohibition of charging interest since it says G-d permitted charging idol worshippers interest. Our Sages strongly emphasize the seriousness of the prohibition of interest - even saying he denies the G-d of Israel as well as the  redemption from Egypt. It is appropriate to try and understand this since it seems to be simply an example of hyperbole. However you must realize that the foundation upon the who Torah rests is the belief in Divine Providence. The Remption from Egypt is a clear example that was witnessed by the entire Jewish people as well as the whole world and reinforced the idea that G-d created the universe and that is why miracles occurred all over the world and were done for the sake of the Jews as was seen with the plagues. Clearly mazel was overcome. When a person engages in farming he has trust in G-d that that which he planted will grow and he will receive blessing. Similarly a person engaged in business has trust that G-d will send His blessings and such are considered Jews since they recognize the G-d of Israel just as they did at the redemption from Egypt. In contrast one who says I will profit from my money he is indicating that wealth is totally natural and not from G-d or mazel or other forces and thus the concept of beracha is limited. The reason one can charge interest to a nonJew is because they are controlled by natural processes so correspondingly you can utilize natural orocesses with him. In contrast a believing Jew who is dependendent on Divine Providence can not be charged interest.