This achievement is on Story Mode - Father's Promise. In the course of saving Amelia after being told by the Soldier in the hospital that the doctor has been taken to the Toy Store, you will go there and 3 insurgents will be interrogating the doctor. Once you save the doctor in the basement and talk to him, the achievement should pop either after you have finished or when you have arrived back to the apartment.
The cheevo popped for me even though I killed the doctor for hesitating and failing to answer my questions when I wanted them answered. I sensed a little bit of co-conspiring in his voice so I decided that I would be the judge on this one and that he did not merit a place in the virtual world of the war that is mine. Harsh but I made my choices.
Credits: CarlosYabrudy