although I think there is a difference between being polite and being positive, I think that attitude it a result of understanding some things...
if happiness is pursuit of the positive rather than flight from the fear-inducing, a happy person must see the positive, and in doing so, learns to appreciate it in typical behavior/reward fashion.
it makes sense that these sort of people, in the end, could feel fulfilled to the point where they no longer need to "take", or in this case, be competitive and "take" something from an interaction with another person
consider someone who has everything, in the truest sense of that phrase, and what their attitude would look like. consider someone who has nothing (and knows it) and consider their attitude. by reacting to the latter type, you are actually skewing yourself towards their unnecessarily competitive behavior instead of away from it. i dont think these people are worth your energy, however, in putting the aforementioned understanding into practice, it doesn't hurt you for them to learn a thing or two from your example