I have never seen such weak FU in my life. You are all worthless and weak.

Firstly, you get the guys email address and head back to your keyboard.

Then, you email him telling him you are the the senior student of <insert Sifu/Master/Coach here> and highly skilled in the art(s) of <insert flashy well know martial art here>.

From there, you tell him that you have insulted you, your teacher and all the brothers that study your art, and that they are honour-less scum, and there is no escaping your retribution, and that of your "family". Feel free to add a few creative in****s abour weeping anii, fat mamas, puss, intellectual disability or even general ****sexual predisposition. Just to show you are a force to be reckoned with.

(Note: make sure you use an anonymous email to avoid any ability to trace your challenge/threat.)

At this point you challenge your enemy to a "no holds barred" death-match on the beaches of Kowloon Island 4 months in advance, so you have time to train yourself up for the meeting by eating small children, and beating live elephants to death with your chi-hardened iron fists of death, and your anaconda like choke holds. At this point you send him one of those gay-boy shots of your half naked torso, covered with rippling muscle. (I can give you a short course in photoshop to get the proper results for only 3x $50 payments if your reply within the next 3o minutes.)

...and you wait.

If they do reply, inform them that the match will be multi fold. Grappling up close, striking at medium distance, kicking at longer range, knives at under 20 feet, pistols at 20-50 feet, kentucky long rifles at 50 to 500 feet, 50cal milspec sniper rifles at 500 to 5000 feet, 20mm cannons at 5000 to 5 miles, cruise missles at between 5 miles and 500 miles, and tactical nuclear weapons at any greater distance.

By the time he gets through that, you should have successfully launched your little bundle of Einsteins joy, and the son of a b1tch should be half way to pink vapour.

If of course you haven't got a tactical nuke at your disposal, just tell him you did your knee and you'll get back to him in a bit.