User blog comment:D.Ryan/Is Sander Cohen dead?/@comment-939754-20100404021633

Cohen will always attack the player if you attack his Masterpiece. It wouldn't be the first oversight in BioShock like it. Chomper's Dental has a button to open the door. The button will ALWAYS spawn Splicers when pressed.

Also, you didn't pay attention to the game's explanation of how that worked. Eleanor obtained Subject Delta's DNA and had the Little Sisters modify the Vita-Chamber system to work with it. She controlled those Little Sisters remotely and, being a non-insane genius, probably JUST made her able to figure out how to do so. I do not think Sander Cohen could have figured out how to do it.