The guy is obviously a disciple of Stephen Krashen, who champions a naturalistic approach to acquiring languages, not learning them. Krashen's theory is that acquisition, which is what babies and toddlers and little kids do when they effortlessly absorb language, works at a subconscious level, which guarantees that any linguistic information you add to your mental storehouse will actually remain there instead of being forgotten, the way memorized vocabulary and grammar rules are quickly forgotten. The natural approach also means listening to comprehensible input (another key Krashen term) and responding to it without being corrected. Learning, which is less instinctive and more deliberate and self-conscious, is less effective, partly because it's more about the work of memorization—memorization of grammar rules and vocabulary, which is rarely enjoyable for folks who aren't language nerds.
And this is where I start to part ways with the Krashenite doctrine. I've written before about how my formation in French was done in the old-school way, i.e., with plenty of grammar charts and writing/speaking drills and exercises. Ultimately, this background helped me speak a rather precise French at a fluent rate of speed. My brother Sean attended the same high school I did, but he went through a more oral-proficiency-oriented approach that was more in line with Krashen's philosophy. Sean probably did learn to speak French at length at an earlier stage in his program than I did in mine, but I have to say that his writing was atrocious because, with nobody bothering to correct his output, much of what he wrote was seriously ungrammatical. This is why I'm not convinced when people say that you shouldn't worry about grammar when learning a foreign language. I get the professor's point, in the above video, that you're better off focusing on fluency through acquisition if your goal is to get speaking the language as rapidly as possible, but I fear that his approach leaves a lot by the wayside—not just consciousness of grammatical correctness, but also basic things like reading and writing, two skills that the professor feels ought to be put off until much, much later.
I suppose how you learn a language has a lot to do with what your priorities are. If you're going on a business trip where you'll need only verbal skills, then of course you'll de-prioritize reading and writing. But personally, I don't see how a person could live and function in, say, Korean society without quickly becoming conversant with hangeul, the local alphabet. (Hangeul does not mean "Korean language," by the way: it means "Korean writing," so if you hear someone say, "I don't speak hangeul," you know that person's an idiot... or at least very poorly taught.*) Hangeul knowledge is what lets you read restaurant menus or subway maps that don't have English translations. It's what lets you sound out shop signs and other written clues that can help you navigate a city like Seoul. Without basic literacy (which will eventually mean more than merely sounding out syllables), the written world around you becomes mere background noise, and you deprive yourself of a chance to delve a bit deeper into the place where you've chosen to live. How sad to remain at a superficial level.
The above video highlights some things I agree with, e.g., the value of TPR (Total Physical Response) as a language-learning tool. As a French major, I took two French-theater classes that greatly helped in my study of the language. Theater, done in the target language, is at least 90% TPR. The TPR curriculum normally involves comprehending commands that are given to you by the instructor, which gives the learner a chance to be exposed to some very common and practical verbs (and nouns!), so I'm a fan of this approach for sure; it represents a type of whole-body learning that you don't get from merely sitting at a desk (although, in the above video, the professor demonstrates a little TPR while seated). And while I do think some focus on grammar and other technical aspects of a language is important, I agree, to some extent, that those aspects ought not to be the central, obsessive focus of one's language-learning journey.
Ultimately, the professor suggests studying abroad, which I also think is the best way to acquire (as well as learn) a language. Your rate of knowledge-accumulation and fluency-improvement will accelerate once you're in a country and culture where your target language is spoken day and night. And it doesn't matter how old you are: as you can see in the video, the professor is no spring chicken (and what the hell is up with his eye?). Just make the effort. A whole world is waiting to open up before you.
*That's as annoying as hearing expats say "us waygooks" when they're trying to say "us foreigners." The word for "foreigner" is waegugin (or technically, oegugin in the Korean government's romanization system). The in at the end means "person." The waeguk part is the adjective "foreign," so a person who says "us waygooks" is saying "us foreigns," not "us foreigners." Idiot. The term oeguk can indeed be used as a noun, but as a noun, it means "foreign country." Oegugin (oe + guk + in) = outside + country + person, like the German Ausländer (Aus + länd + er: outside-country-person).