I think one reason that these sorts of discussions generate so much argument is because of the natural human tendency to dislike
uncertainty. As martial artists, we devote ridiculous amounts of time and energy to our training. (Probably over 7000 hours of my life so far in my case.) We'd like to feel that all this work should have some sort of guaranteed payoff in ensuring that we can defend ourselves.
The problem is that there are no guarantees. The world of violence is huge and varied. What works in one situation might not be useful in another. No one is expert in all of it. Given the constraints of legality, morality, and practicality - no one
can be expert in all of it. This tends to be an uncomfortable truth for those of us who have devoted so much of our lives to training in the martial arts.
I'm going to pick on Mook for a minute, even though (based on footage he has posted) I believe that he is a skilled martial artist who could probably handle himself well in many fight situations.
Mook chooses to believe that Wing Chun practitioners hit faster and harder than everyone else - to the point where they can't safely fight full contact without the serious risk of killing or crippling their opponents. He believes this even though plenty of Wing Chunners over the years have taken part in challenge matches, street fights, and even MMA matches without ever killing or crippling anyone. To an outsider, his certainty on this matter resembles a matter of religious faith - needing no proof and immune to disproof. I suspect this is because he (like all of us) doesn't like the uncertainty that comes with not knowing for sure.
I'm going to pick on Hanzou for a minute, even though he is a fellow BJJer and I agree with many of his ideas concerning effective training practices.
Hanzou chooses to believe that MMA is the ultimate test of what works or doesn't work in any violent encounter, even though many real-world violent situations have very different circumstances from what happens in the cage and those differences can greatly affect the techniques, strategies, and tactics which will be effective. I suspect this is because MMA provides something knowable. You can watch a bunch of MMA fights and end up with a pretty confident assessment of what will or won't work without all that pesky uncertainty.
My personal approach is to gather as much knowledge as possible from every source. I watch MMA, kickboxing, and grappling matches. I watch the Dog Brothers do full-contact matches with weapons. I watch videos of street fights and street assaults. I read accounts of different sorts of violent encounters and crimes. I listen to police officers, prison guards, and bouncers talk about their experiences. I spar under all sorts of different rulesets. I do scenario training with various rules and scenarios. I try to analyze how what works changes and what stays the same under different rules and circumstances and extrapolate to figure out what might work under different circumstances. I note what sorts of situations are well-documented with lots of examples and which are not. I accept that my understanding of the less-documented situations is always going to be uncertain and provisional. I accept that everything I think I know is subject to disproof at a later time. It's not as reassuring as thinking that I have full understanding of what works and what doesn't, but it's more reality-based.
(Note - the link at the start of this comment leads to a blog post I wrote a while back about uncertainty.)