Sometimes our truest intentions are unrealistic, so people choose to take the good with the bad, but the moral intention remains the same regardless of the means to that end. It is why someone might experience guilt or uncertainty over what they believe to be the best course of action in a given situation, or not, if they are convinced they are doing everything in their power to align with their good intention. Most of the time when people say they want a specific outcome, they are actually searching for a way to get something else, not the outcome itself. A person who is unaware of all their options--or whose options are limited--might rationalize their actions for this reason. Some people are also more impulsive, and may not think through the aspects of their decision that could result in unintended consequences. On the other hand, the world has people who deliberately sabotage others for personal gain and to protect their egos. I think less people would sympathize with someone like that because they don't relate to the lack of empathy if it's not the norm in their environment and is seen as a threatening behavior.
Another interesting thought--every moral dilemma boils down to the fact that each value has its own subjective weight, which is why we can perceive someone else's views as extreme, even if they stand for something we regard as good (high-priority value). I think morality and the scope of our empathy are conditional at least in part upon our perceived needs and fears (the other factor being our natural empathetic ability), and whether embracing certain values supports those needs being met. For example, our species has a lean towards cooperation as a survival strategy, so we encourage it as "good". A need can also be something intangible, like an abstract feeling which is psychologically beneficial to the individual.
