Based on my experience and many cases in my country: Never accept any sparring / duel fight challenge outside formal fighting tournament event.
Duel fight challenge in real life is totally different with video game or anime. In real life, there are lot of cheating often done by the challenger.
For examples:
- In 2009, Muay Thai was became trend and booming in my country. Sadly, not all Muay Thai gym owners are good person, many of them also doing ilegal side job as hired thug.
Those bad Muay Thai fighters often challenging other “rival” dojos to show off their “power”. In several cases, they also using iron plate filled Boxing glove or unpadded Boxing glove to kill their opponent (like Luis Resto and Panama Lewis case).
- Many barbarian Silat schools are also often brawls each other on street and ilegal duel fight. In many cases, the dueling fighters often using hidden weapon like pocket knife or spiked ring to piercing their opponent.
- When 1 dueling fighter cornered, his friends will come suddenly (mostly riding motorcycle) and will start attacking the rival school. The duel turn into ordinary gang brawl.
"Then what should we do if someone challenging us for duel?"
- Reject and expel him outside from our dojo. Martial art is just for cardio exercise and self defense.
- If they won’t leave, call the security or police. My Karate sensei doing this once when some Muay Thai thug came to his dojo.
- If those thugs start attacking, then it’s time to show them what we got from our training. It’s self defense situation, of course police will arrest them for assaulting our “private property” first.