I overheard two mums in pg just now, one of them was saying the "boys being boys thing." Both mums have boys in DS3's class who are regularly in trouble for hitting/kicking/generally being horrible to other children in the class. They were the same at preschool.
No it's not boys being boys, I have 4 I should know, they have their moments granted, but they do not regularly hurt other children.
In this case I would have rephrased it as "it's just boys being thugs and getting away with it AGAIN!!"