Why do 'good' people do questionable things? Who really knows?? But, here are some reasons:

• If corruption, major or minor, is a part of the workplace or environment, people often become blind to its occurrence and its possible costs.

• Cognitive dissonance and rationalization.  When people's actions differ from their morals, they begin to rationalize both to protect themselves from a painful contradiction and to build up protection against accusations.

The bigger the dissonance, the larger the rationalization, and the longer it lasts, the less immoral it seems.

• People compare their present behavior to what they've done in the past. Another way people slide down the slope of unethical behavior is to stop seeing that behavior as bad.

As the unethical becomes routine, the extremely unethical, once unthinkable, enters the realm of possibility.

• Sometimes people, having been moral and forthright in their dealings for a long time, feel as if they have banked up some kind of "ethical credit," which they may use to justify immoral behavior in the future.

• If a conflict of interest is publicly disclosed, it can seem less problematic, as if it has been agreed that it's all right. That can lead people to indulge their bias.  

• In order to fit in with a group, people do things they might not otherwise. That can lead them to ignore abuses for the sake of peace or unity and go along with questionable decisions. 

Children who've been brought up with parental commitment to avoid using the word 'No' ...viewed as psychologically damaging, what kind of adults do they become??  Likely they will have a broad scope of accepting behaviors they are practiced (or learned) in rationalizing. The things they don't accept are those things which have limitations set upon them ...which they view as intolerant.

While kids almost always appear to beg for controls, limitations, and confident guidance during their childhood ...later on, (if there had been an absence of it early on) there seems to be resentment and anger towards any attempt to introduce it. (http://couldshouldwouldoneisgoodwhoisthree.blogspot.com/)

In considering 'the end justifies the means', I view it as only God being qualified to justify anything. (http://canbeinginsinbeadvantageous.blogspot.com/)