Wrong! You need both (martial arts skills & a gun/knife) to defend yourself effectively.
I'm good. But the majority of others are likely to suffer from one of the following conditions: obesity, old age, drug or alcohol, some sort of debilitating injury whether it be a bad back, bad knee, hip, shoulder....
Physical fitness can help all of these factors but and you do need to be fit to defend yourself when your gun or knife is not there, but it takes time to get physically fit. You aren't going out there tomorrow or in one week of work and able to defend yourself. It takes time. It's something that should be as secondary as playing football, basketball, double dutch (for the girls), riding a bike.
So many are so far gone, they might as well gone head and get a Glock, if they are eligible.
But definitely continue to work toward fitness.