ARGUMENT OVER PUP AGAIN AAARRRGGHH WHOZ RIGHT?

my partner bought a 6 week old pup from a rescue centre two weeks ago.ive said to him it must of come from a puppy mill because they dnt usually leave their mam till their at least 8 weeks old.hez shouted back to me that it wont be from a puppy mill because it was bought from a rescue centre and he says they are registered breeders.i made the point of saying that if it was a true registered breeder they wudnt of let pup go so young wud they? can sum1 settle the argument plz... he says if i dnt shut the **** up im going to get summet thrown at my face