Re: MBA "Qualification"
It does seem there is a propensity for MBAs to believe they have sufficient qualification for running a business of any kind
You confuse cause and effect. An MBA is a piece of paper that shows you've completed an accredited training programme. As such it is similar in concept to an IT course, or an NVQ in cleaning.
Your logic comes across as "I've met a few people with MBAs, they were arrogant, ignorant and incompetent, so many/most/all other MBAs will be the same". That doesn't seem very scientific nor likely to be a statistically valid sample, and to assume that the people concerned behaved this way because they have an MBA seems to be a matter of wanting that to be the case universally, because you are unhappy with your experience of a small number of people.
As an MBA is a qualification aimed at middle and senior managers, it is at risk of attracting self important twits, but when I did mine, every course member came from a functional background, with the knowledge and experience to prove it. Sales, finance, IT, operations, logistics etc. And the MBA I was taught was specific that it wouldn't make us experts in anything, rather that it would teach us the limits of our own knowledge, with sufficient education to hold a sensible conversation with those who really did know their stuff in other business areas.
Now, as with any qualification, if somebody's a complete ****, they can still earn a qualification, but at the end of it they'll still be a complete ****. But its very unlikely that the qualification made them a ****. I suspect that if you've experienced poor standards of MBA qualified managers, that is probably more representative of severe organisational culture problems than evidence of a problem with the MBA (or any other qualification).