Both legal fallacies.
The idea originated to express a point that one who is a martial arts expert can HURT/HARM another more in a fight, where an ordinary person could not, so the expectation of “reasonable force” “may” be higher for them.
Well, I also remember hearing of the response, “I know karate, judo, jiujitsu, taekwando, …and a lot of OTHER dangerous words!” 
NVM. The joke’s better only when told once.
I used to be in the SCA, and we had regular social events on Saturday mornings in a public park. Every other month or so somebody would call the police and report a bunch of weirdos running around with swords. Almost inevitably the black and white would pull up next to our meeting spot, the officers would come over to take a look, and they’d spend the next half-hour checking out everyone’s swords and armour and dying to try them out.
I’m just a confused Canuck: I thought he wanted to disarm people…
[moderator note]
Obviously, you realized it would be taken as a political jab, or you wouldn’t have included the disclaimer. Keep the potshots in GD or the Pit.
[/moderator note]
Most people trained in karate who run into an experienced street fighter get pounded into mush. Martial arts is some pretty stuff but you have to lose a lot of blood and replace it with anger before you’re a threat on the street.
Better would be
“I’ll give up my hands when you pry them from my cold dead arms.”
If you’re talking about strip mall martial arts schools, with instructors who have 3 or 4 years of training, sure. Otherwise…plenty of martial arts schools train in very practical fighting as well as the more flowery stuff. I’ve taught and practiced martial arts for years, and I ASSURE you that the dirty tricks that streetfighters learn the hard way are also taught in plenty of martial arts schools.
But sure, there are plenty of 13-year-old “black belts” who aren’t much in a real fight, because they’ve only trained for 2 hours a week for 4 years. or some such. The generalization doesn’t hold across the board, though. If you disagree, I will be happy to direct you to plenty of people I know in the martial arts community who are plenty savvy about real-world deadly situations.
Do you have any actual martial arts experience?
I know *somebody *who ain’t gonna be no clown in the rodeo!
I love reading stuff like this. After a long, tiring day, I need a good laugh.
Brief Q & A during Law Enforcement Boarding Party Training (USCG)
Q: Will we be learning karate?
A: Karate is great, but with ka-colt .45 acp you can drop the sucker at 25 yards.
Spoken by someone who is neither a black belt, nor a street fighter.
Weren’t most of the guys from Street Fighter black belts?
Archer:The Dane Cook of martial arts?
I don’t think Blanka owned a belt.
Oh now, the guy’s only 5’-10".
6’-6"/180 is not all that scary looking. If you exaggerate height, you need to exaggerate the weight to match. 
Better still … cold dead guns.
The only objection that I have to that is that sometimes the ka-colt isn’t available. The body always is.