It's largely inference. Floyd's shrink nailed Floyd's self destructive habits, but observed that a part of him didn't want to die, didn't want to lead this life. This is seen when Floyd re-enacts his trauma with Rick Flag, obeying his 'mother' and in his (insane) eyes, correcting the mistake he made as a kid.
In the Suicide Squad, Floyd only had a few special relationships. Flag was his brother, Waller was his mother, his shrink mighta been a love interest and really, that leaves Batman as his absolution. Which given the contrast in their origins, makes the most sense.