Depending on how conservative your workplace is, you may not want to watch this clip at work, especially with the sound on...
The first time I watched this clip, I watched it with the sound off, which is something akin to watching The Wall with your eyes closed. Watching it muted, I was impressed by his strength and power generation. I was also impressed by his student/target taking so many shots on camera without complaint.
So, imagine my surprise when I watched it with the audio a week later!
First off, aside from my biases not expected an English accent from Master Wong, I was surprised to hear his strong language. In fact, I stopped and scanned back to replay a section to verify what I'd heard. Master Wong had caught my attention. And now I was laughing quite a bit. It's now an inside joke with my students to "f'ing taaaaaaaste the power!"
I've been known to use the occasional swear word in class, which is problematic when teaching in the YMCA, so I try hard to keep it in check. I do appreciate his sense of humor though.
His skill and presentation aside, I can't help but remark on the fact that his assistant is getting clobbered. Gear or not, he's gotta feel that. It makes me think of my teaching style, and how other instructors I know feel the need to dispense great amounts of pain on their compliant partner. I've seen instructors seriously injure their students, cause brief flashing pain and sometimes just hit them for the sake of hitting them.
In any other environment, this would be met with complete shock. But in the dojang? You see some evil smiles and giggles. Is it how we cope with seeing our fellow students getting thrashed?
Why do we as instructors feel the need to punish the volunteer? Is it to prove the effectiveness of the technique? Is it to prove OUR ability? Is it to show why we're at the top of the dojang food chain? Is it a way to give passive-aggressive revenge on a student who is annoying you? Is it any, all or none of these things?
I can't say in your case. And I'm not trying to say that demonstrations need to be free of contact pain or slight (albeit controlled) risk. I just want people to think about why they demonstrate the way they do. If it's for some of the reasons I listed above, maybe you should think twice before landing the punch.
Side note: Master Wong has an extensive curriculum on Youtube that he shares for free. If you're interested in Wing Chun, check out what he's doing.