Washing their hands like Pilate? providing the means for the scam to carried out and profiting from it?
I could see how they would make a case for added coins that they have no control over the premine etc. But this one is different, this was carried out in their "premises" under their jurisdiction, the thief has been caught in the process and is linked to two crimes being performed within the same day, that's close to $200,000 in fraud!. 

It is in Bittrex best interest to protect its fragile userbase from such obvious "attempts" (attempt because Bittrex still has the last word), it is now that Bittrex must act and show what code of ethics they operate on.