In Chinese, we have a saying "Think of the source, when you drink the Water". In that way, you can enjoy and understand the full flavour of the water and learn to respect each others.
I have met many so called "Martial Artists" my art is better than your Kung Fu and etc...
Any serious Martial Artist would have studied the founder martial art background in his or her chosen art.
Because by drinking Japanese or Korean or Thai water, it does not mean that water source didn't pass through or even came from China.
China never claim all martial arts are originated from China, but there is facts that many systems are either direct or indirectly influenced by Chinese over 5000 years old system. (As a matter of facts, China civilization has indeed influenced many system around the world, not just in Martial Arts).
Of course, through evolution of Martial Arts system many has added local falvour or some even became unique system. That is the beauty of Martial Arts evolution.
So next time before you challenge other arts, you have to find out your source first. And also which Kung Fu system, because there are hundred of Kung Fu Systems.
Anthropologist claim we are all children of africa, what do you think?