I don't think that your friend considered his remark to be a joke worthy of a laugh, but it sounds like "good natured ribbing" over something entirely benign.

I don't think that your friend considered his remark to be a joke worthy of a laugh, but it sounds like "good natured ribbing" over something entirely benign. It's a social technique employed by many people on a day to day basis as a bonding method where no offense is usually intended and no offense is usually taken. Where your friend failed, in my opinion, is that he should recognize that not everyone is receptive to or appreciates this kind of teasing. It's up to him to identify the "line" that should not be crossed with some people and then not cross it.