There is nothing to punish here, for insults like that on default/priv you can use the ignore function.
edit: ill briefly share with you my school of thought so things don't get distorted
being brazilian and using that sentence thousand times in my life have taught me that you never use that to offend someone's mom, there are more effective and direct ways to do so.
"filho da puta" is mostly used to call someone a disrespectful/garbage/bad person, even if the literal translation is "son of a whore", it aint meant to offend anyone's mom but to offend a specific person(in this case the disrespectful player).
i believe it has the same effect as "hdp" in spanish.
since generic offenses like that on PM or default aren't punisheable, nothing we can do in this case.