Agreed. Having opinions in an area in which he is totally ignorant, and being too arrogant/stubborn to admit he's wrong does now equate to mental illness.
(I assume you meant "not".)
Yeah, I agree. Otherwise much of the world would be considered mentally ill.
There is an intriguing phenomenon called "folie a deux", though sometimes "deux" can be a very large number.
I've actually seen it at work. My sister and the kid down the block would get in far more trouble together than apart, to the point that I, when we were kids, referred to them as bad influences on one another. It wasn't to the point of mental illness, of course, though they did almost set our neighbour's backyard on fire once playing with matches in tall, dry grass.
If he genuinely believes the things he is saying then I would agree he is not a well man, but there is no evidence he is risking harm to himself or others (his claims to be a safety consultant are clearly false, as his 'company' webpage is nothing of the sort and no official body recognises him as such), therefore no need to section him.
I'm willing to leave the decision to the proper authorities who can examine him personally, but just because no one is using his "professional" services doesn't mean he is harmless. Just the idea that he is his usual realitydenying self, while driving a car makes me glad he is not near me...
But you have no idea if his reality-denying extends to the operation of a car, and it almost certainly doesn't. After all, most people in the industrialized world grow up with enough cars around them that their operation is pretty intuitive. Cars are a part of our natural environment, and everyone knows how they work. Most of his greatest errors have come from things that aren't intuitive. Besides, if we're going to eliminate all the bad drivers from the roads, it isn't just going after the mentally ill.