This achievement was giving me fits. Apparently, the right answers aren't so obvious to me
I found a video, which you can watch here
I will list the dialogue choices by chapter.
Chapter 2 One of Us-Drink tea
-Correcting paths?
-Not the same cause
-... (this will be the only time you ever respond with silence)
-Open it
-Does it matter?
-Redeem?
-My interrogator
-Assadollah Lajevardi (he will smack you, but that's fine)
-Hajj Agha
-Just a photographer
Chapter 7 Big Brother-Tell me more
-You had a cause
-I'll talk!
-He was foolish
-Yes
-Yes
-I don't know
-Are you serious?
Chapter 12 Pulled the Trigger-Then show compassion (he will shove your face to the table, also fine)
-You have it easy
-I've made mistakes
-A free Iran
-Anything is a weapon
-I'm sure you'll tell me
-I didn't realize
-Okay, fine (this and the last will be to Hossein)
-I had to hide
After all that, load up
Chapter 19 My Brother's Keeper (which has no dialogue choices) and when it ends, the achievement should unlock.
I can't say for certain that this is exactly what you have to say, i.e. there may be more than one acceptable option at times, but this worked for me.