This is my last try since this is going so wildly off topic.
Knife fighting is not a subject we care to discuss here for obvious reasons.
The Ka-Bar was not a fighting knife exclusively - it was designed as a combined fighting/utility knife (information freely available on the Ka-Bar website) and most people I have spoken to who use them, including past military users, have been far more concerned with the utility side of things for establishing camps etc.
Most people with more than an ounce of common sense are able to make an informed decision of their own. With the greatest of respect to Mears, Kochansky et al, if they all suddenly said a 5, 6 or 7 inch blade knife was the ideal there would be the inevitable stampede for the latest must have while the rest of us sit on the sidelines having long since adopted the stance that there is no ideal in all situations and conditions and that any attempt to make one is nothing more than a trade off of the highest order.
Large knives and small have been used by most peoples throughout the ages. The Bowie, in most of its various guises, is, in fact, little more than a Scramasax or Seax if you prefer, which was the standard working knife of its age and sizes ranged from the huge to the svelte.
Can anyone say with any certainty that "The notion that a heavy hunting knife can do the work of a hatchet is a delusion" ?
That's codswallop.
At least nine times out of ten I would take a larger knife over a hatchet any day of the week and I know a lot of other folks of a similar mind. For those who prefer the hatchet I have no problem with that - it's a personal choice based on what you can make work best for you, not what someone else tells you to think. There's a bit too much of that in the bushcraft world, frankly.
What I can say is that everything I can do with a typical hatchet I can do better or at least faster and more efficiently with a larger knife with the exception of using the poll for a hammer (only on soft materials, not on metal).
A large axe is useless unless you are going into log construction, a small axe is of limited use to most but sometimes handy to have, and both are usually outperformed by any one of a number of modern manual saws.
The original question (for those who seem to have overlooked it) was that the individual concerned has one of these knives and is interested in possibly using it in an outdoors scenario. How we made the quantum leap to knife fighting, small knives only, tenderfoot labelling and so on is beyond me.
20 years ago folks were making 5 - 8 inch Bowies, the odd (significantly) bigger Bowie, an occasional up-swept skinner and a lot of drop point hunters. If you made anything else with the possible exception of Tanto style knives you didn't sell them. The owners of those knives managed bushcraft and hunting activities with them just fine, and this was before anyone knew what a Mora was or that they really should be using something else.
Here in the UK most of us grew up with the leather stacked small Sheffield Bowie knives that were about all you could get your hands on, but we hunted, fished and generally got up to no good in the outdoors with them all the same.
The very best butchering job I ever saw was by a vet who used a Swiss Army folding knife on a large Elk.
I have been guided on hunts in Canada and Alaska by people toting anything from Chris Reeve one-piece hollow handled knives, hand forged, or stainless, or Damascus and, once, by someone who used a Schrade Sharp Finger and, boy, was he ever good with it. I doubt he even knows who Mors Kochansky or Ray Mears is or, if he does, I doubt he much cares what they have to say about his preferred choice of cutting tools. Given the guides respective expertise and the simple fact that they make their kit selection (both large and small) work for them, who would I be to question it ?
The leuku example above is a great definer - it pre-dates the Bowie knife by a very, very long time and is the de facto standard to Laplanders. They, coincidentally, know a thing or two about living in the bush and they were using their leuku's until very recently for that purpose countrywide - some still do.
This has become like any one of the pointless arguments over calibres, or longbows v compounds for hunting, or...
I think a key point is missing here - I think the 'adapt' from "adapt and overcome" has been well and truly dropped. Almost anything can be made to work well enough, if you choose to give it a run.
Ka-Bar: not everyone's cup of favourite beverage. Can be made to work very well for those inclined to do something useful with one, and will never work for anyone who can't see it through the right eyes. If you have one and want to try it you might be pleasantly surprised. If you're not, clean and oil it and put it away or move it on, but at least you get to make an informed choice based on your own thoughts and experiences with it.