Edward, surely you mean if you're a thug then you should not be allowed to train. There is a big difference between a thug and a well trained capable martial artist, or at least there should be. I see nothing wrong with training purely for practicality. It's not the only reason I train, but it must be present otherwise people who think they are learning a martial art are being short changed. I believe the ki, harmony, etc aspect you alluded to are developed through hard constant training.
All the best