On the topic of common courtesy

The other day, in a discussion about politeness, I was lead to say something, which initially made me happy, but ended up frightening me.
It began with the finding that even though all people seem to have less time these days, this is no excuse for rude behaviour - hereafter, the recognition that because common courtesy does not cost any money and does not take much extra time - well, there is no reason why not all people are polite. All in all quite well. Thus the happiness.
But then I came to think: since there are actually rude people who do not observe common courtesy, there can only be one of two scary reasons for it: either they are not brought up to treat other people with kindness, or they actively make a choice to be rude.
I do not know which one is most scary. But I know that if you are treated politely and with kindness, it tends to rub off. So, hereby a call to all of us to exhibit kindness and common courtesy towards other people at all times.
Not to say that we can not disagree. But let's do it respectfully.
(Translated from Noget om almindelig høflighed)