The assault came after the 58-year-old spied a text between his wife and the friend about
their love for each other.
Judge Brandts-Giesen discharged the man without conviction, saying it was a "nasty assault" but that it had to be seen in context.
"Really, this is a situation that does your wife no credit and does the [male] no credit,"
the judge said in sentencing.
"There would be many people who would have done exactly what you did, even though it may be against the law to do so.
"I consider that the consequences of a conviction are out of all proportion to what happened on this occasion."
Victim advocates were furious at the comments, saying Judge Brandts-Giesen showed a complete lack of understanding of domestic violence".
He was also accused of victim-blaming and "minimising" the severity of the assault.
Chief District Court Judge Jan-Marie Doogue also commented on the sentencing.
It is extremely rare any other judge - let alone the top District Court judge - to comment on the actions of their peers.
Judges are independent and as such, do not have to justify or explain their decisions.
"I cannot comment on the case at this stage because it may be the subject of appeal," said Judge Doogue.
"But to the extent that the Judge may have expressed himself inappropriately in any event, I do not seek to defend his remarks.
"And I am sure on further reflection neither would he."
New Zealand has the worst rate of family violence in the developed world, and in recent years the police have ramped up efforts to reduce and prevent it, and to raise awareness and encourage victims to report violence.