You should always be polite, you might meet them again in a different time and place. It sounds like this rejection bothers you a lot. You are in danger of not seeing the bigger picture because you are hung up on not meeting that single requirement.
It doesn't bother me that I didn't get the job that much. Just the headline of this thread reminded me of it. I already had a comfortable position and I have a new position now in a great team. I think it worked out for the best.
The only way in which this bothers me is that these (I assume) fake, unfilled jobs are used for political reasons. But that's a global problem.
