When any animal, including humans, is trapped in a situation they can't escape, failing to adopt a degree of acceptance is bad for their health and survival. Almost all other animals will stop fighting after being held captive for a while, so why shouldn't humans?
When people do bad things they almost always have a reason for it. The reason may be sick, twisted, or wrong. Its 'justification' may be prohibited by our culture and for good reason. The causes of their actions may be, a lest from some perspective, an inevitable conclusion of forces which they felt they could not control. An open mind could often understand why or have sympathy for it, even if they continue to disapprove in the strongest way possible.
Humans are very social and often become friendly with people they spend a lot of time around or interact with a lot. Even when they start out with very different views or places, or with a profound disagreement.
In plenty of situations outside of captive abuse people sometimes fall into the trap of becoming addicted to abusive treatment, be it the rare bits of approval or reprieve from the expected abuse, or simply the fact that they're the center of attention (even if its negative attention). -- if you've not seen this happen first hand, I envy your sheltered existence.
People outside of a situation are also not blameless. Why didn't they prevent it? Why didn't they rescue the person sooner? Why can't they understand how significant the event was and why can't they understand how significant the event wasn't? Why can't they accept that you do or don't feel defined by it? I think it would be easy to feel worse about the people who let you be taken hostage than the hostage taker, the hostage taker owed you nothing, the hostage taker wasn't in a position of trust, the hostage taker will suffer retribution for their acts, but perhaps the people who screwed up preventing it will be called heros.
So with all these factors at play why should any out of a wide spectrum of responses to a adverse situation not be considered perfectly natural?