Nishkama Karma

I am reading this book called "The Difficulty of being Good" by Gurcharan Das. In the book, he discusses the merits and non-merits of the concept of "Nishkama Karma" or being a "Karma Yogi", as put forward by Krishna in Gita.
He raises some interesting points. Like, the good think about doing something without caring for the fruits is that you can lose yourself into the task in hand, without getting diverted by thoughts about whether you will be successful, how your work will pay back, what will be the consequences. This can result in a better concentration and efficiency in the task. On the other hand, not thinking rightly about the results, and stifling your emotions to perform your duty can be dangerous. As, Nazis happen to justify executing millions of jews as "performing their duty for their country", although the task in hand seemed hateful. So, perhaps more jews would be saved if the individual officers worried about the consequences, and hateful nature of the task.
My take on this is, once you have decided this is what you are supposed to do, or this is what your duty is, you should then become a "karma yogi". Because doing anything with full heart is better than dillydallying whatever the nature of the task might be. Although, a difficult thing to do...