Many years ago I worked with two guys. One was a high ranked taekwondo youth champion, and the other had learned to fight on the streets while he grew up in a rather bad hood. The taekwondo guy was always bragging that taekwondo was sublime to any other martial art and that any street fighter would lose a fight against him (this was way before MMA). One day the streetfighter said "Ok, if you're that good, prove it !".
Then we all went outside, and watched the "fight". The taekwondo guy did some very impressive roundhouse kicks, while he was saying strange noises, but every time he kicked, the street fighter just took a step backwards. He ended up with his back towards a wall, and everyone held their breath, waiting for the final kick. Then the street fighter took a deep breath, stepped forwards, grabbed the leg coming towards him, and with one single punch broke the nose of the taekwondo guy. Then we all went back inside
That somehow lowered my respect for martial arts slightly, until I saw Royce Gracie in the first couple of UFCs.