It is often said that trying to learn via instructional books or DVDs is a fool's errand, and will yield no fruit. When someone cites that they are effective with a weapon they learned by one of these means, they are told they are wrong--they are, in fact, very bad with it, and must be lying to us or themselves.
The reasoning is usually that anyone who created the book or DVD has obviously studied with a teacher, and thus studying with a teacher is really the only genuine way to learn. And those teachers studied with teachers, and those teachers, and... wait...
That's right. If you go back far enough with ANYTHING--weapons, musical instruments, automobiles, folding paper airplanes, whatever--you find that it was originally hashed out by one guy trying stuff. He may have used other existing and similar devices as models, but in the end he had to just try stuff.
Then he taught some buddies, and some of them tried new stuff and refined old stuff. Then they taught buddies. Then buddies started writing it down.
Instruction is not magical, and having a good teacher will not make you any better than anyone else on its own. Instruction in all things is simply a shortcut to save you, the learner, a lot of trial and error--or at least make sure the "error" part is less frequent than it could be. But it is not the sole means.
Even as a music educator, I can admit that there are plenty of self-taught musicians that are phenomenal, world-class performers. Does that mean my job is unnecessary? Of course not--not everyone has the time or desire to self-teach, and some people want to be part of a larger community of musicians and should thus learn the standardized language. Does it mean that my students are bad musicians because they "needed" a teacher and this other guy didn't? Not at all.
But THAT is usually what happens here. Someone with years of instruction is INSULTED that someone else wants to take the "shortcut," or (let's be honest) simply doesn't have the option (time, money, availability) of true instruction.
Is the would-be learner here to insult them? Not in the least. He's here because he has no option, but he wants to learn (and being a conscientious learner is just as important as having an expert teacher), his options are slim, and he wants opinions on the best way HE can do it. And let's face it, a book or DVD =is= better than no help at all.
What's more, some people (through study of dance, gymnastics, or martial arts) have a better awareness of body, and some of the more subtle nuances they MIGHT just pick up instinctively. Or they'll get them through trial and error, like millions of people have done before them.
Teaching isn't about "making you learn the way I learned." It's about showing someone how to learn. EVERY, and I mean EVERY good teacher has a goal of eventually empowering their students to TEACH THEMSELVES--we are the only job who hopes to make ourselves obsolete.
And all we, as teachers, do is provide a model and then troubleshoot while you try to imitate the model. That's it. We show you how it's done, then watch you try to do it, help you find your mistakes and fix them. A book and video can provide you a model, and as you learn, you'll be able to go back and find mistakes and fix them--and discussion with other people via the internet will help, too.
So, yes, you CAN teach yourself. ANYTHING. If you're willing to devote the time and bruises, you can learn it. It's simply a question of 1) will and 2) goals:
When it comes to the will to learn: Are you able to admit your mistakes, and LEARN from them rather than COMPLAIN about them or get discouraged? Are you willing to experiment and be wrong MANY times before finally getting it right?
When it comes to goals, remember that no goal is inherently "wrong." Is your goal to learn just one form so you can look and feel cool? GOOD! Do it! Your goal isn't to use it for combat, so knowing the intricacies of application isn't necessary for your goal--and you can always learn that later if you find your goals change. Is your goal to be able to scare off prowlers with a few choice moves? Learn them and leave the rest--you don't OWE anything to the arts, as the arts exist to serve man and not the other way around (be careful that you don't take advantage of PEOPLE, though).
The bottom line is: Don't be a student elitist. Just because someone is self-taught doesn't mean they're worse than you, nor does it mean they think they're better. It's no different than a student that learns quickly and one that takes a few more tries--both can get it equally right, and the only difference is time.