לזכות ידי"נ הרב משה גבריאל בן יהודית לברכה והצלחה בכל מעשי ידיו!
The Chofetz Chaim writes [4/12] that
if one speaks lashon hara and his words are accepted by the listeners then he
must do teshuva as for an aveira bein adam la-chaveiro but if his words aren't
accepted then he must do teshuva as for an aveira bein adam la-makom.
It emerges from his words that one is
only guilty of an infraction of bein adam la-chaveiro when he harms his friend in
some way – monetarily, his honor or
otherwise. But, as they say on the basketball courts, "no harm, no foul"
[I used to play in a rough neighborhood where the rule was "no death, no
foul"], at least on a bein adam la-chaveiro level.
Rav Hunter asserted that this is not correct.
When one acts against his friend it is a breach of bein adam la-chaveiro
regardless of the outcome.
There is a proof for this assertion: The Chinuch
cites the Rambam as saying that when one curses his friend it doesn't harm him
but is forbidden anyway. Yet the Rambam paskens that when one curses his friend
he must ask forgiveness from him. So we see that even when not causing actual
harm but just acting in opposition to his friend is enough to qualify as a breach
in Bein Adam La-chaveiro.
[ספר זכרון עמ' שלה-שלו. ועי' בס' ביאורים ועיונים על ב"מ עמ' רמ"א-רמ"ב שניסה ליישב את דברי הח"ח].