A beautiful example and a wise and generous move.
He knew that he was on very thin ice, sh@t himself and backed down. JKR accepted his apology. (As she does for with everyone who doesn't double-down.). She's very much "live and let live". Now, if he leaves her and other gender critical people alone, she will leave him alone. She's made her point,
If and when, one day, anything ever gets to court, it will be seen that she is very reasonable, and not going looking for trouble, unlike some other individuals who push the envelope over and over again.
JKR is not contentious - but she isn't a coward either. She knows when to stand up, and when to (graciously) back down.