In the heat of the moment it's barely excusable regardless of who say it. For many years this type of talk has been allowed to fester in Origin. In the NRL, a day later - it beats me how it's not slander. When Bellamy and Waldron made similar comments about the judiciary when they suspended Cameron Smith in the 08 finals, legal action followed.
I suggest that the NRL let them off because of the wrong doing and the history of the Cowboys recent finals exits, coupled with the hullaballoo from up north, which is fuelled by the long running Origin sledging such as Meninga's "Rats and filth" and Mason's "Nutjob Rednecks" comments, Lockyer's lack of grace toward NSW in his speech after the "Price Road Kill" Origin, and a thousand other incidents where sportsmanship has been ignored in that arena. That's one reason.
The other is that the NRL are softcocks who have no idea to deal with such issues with justice, level headedness and humility to the victims.