[Avodah] charging ribis to a Jew / non-Jew

[Kelmar, Michael J.]

R' Micha Berger wrote: "WRT ribis, the pasuq implies what the difference
is when taking ribis from a Jew vs taking it from a non-Jew. It uses the
word "achikha". It's not that ribis is inherently immoral, it's that
brothers don't charge brothers interest."

Fahr vos nisht?  Do brothers not charge brothers 5 cents for a gum ball?


Also, I do not know what the phrase "inherently immoral" means.  Please
provide some hesbir.