I completely agree with the author. It is important that language has precise meaning if thoughts and ideas are to be passed down through generations. I believe the founders meant to convey, "Because a well regulated militia is necessary to the security of a free state, the right of the people to keep and bear arms shall not be infringed." They might have been careless in their language, but I don't see how any objective person could interpret it any other way.
It's been over thirty years since I sat in a Latin class, but I seem to recall that this sentence structure was quite common in Latin. I believe that it was called an "ablative absolute". I don't believe that our Founders had any doubt about its meaning nor were they in any way careless.
A closer reading than yours might be:
"Because, among other reasons, a well regulated militia is necessary to the security of a free state, the right of the people to keep and bear arms shall not be infringed."
If anything, this reading still too strongly connects the two clauses.
Here's another example:
"The sun having risen above the horizon, the captain ordered a ten minute rest break."
The sun having risen did not CAUSE the captain to order a break. It was more of an indicator that he should. It doesn't mean that there aren't many other reasons why he might have called a break. If anything, it is closer to a grammatical structure consisting of two independent thoughts connected by an unstated relationship. The weakness of the relationship is because it is not critical to the meaning being conveyed. This sentence structure should have been a cue to the Supreme Court that it was intended for them NOT to find the connection essential.
Unfortunately, I believe that the Supreme Court did exactly what the Founder's choice of sentence structure was designed to avoid. If our Founders had omitted the Militia clause, then the Supreme Court would have concluded that our Founders could not possibly have meant that the populace be armed so as to be able to overthrow the government. The writings of our Founders show quite clearly that that is exactly what they intended.
I think it is a duty for every able bodied citizen to maintain a military style rifle and be proficient in it's use. You just can't tell when things might go completely to hell so you might as well be prepared. It has just become habit for me. In the Army I spent 9 years of my time being in a constant state of readiness to deploy. In Montana we have a very high proportion of militarily proficient citizens that can be depended on. They are loyal to the state of Montana and to the President, but most especially to their neighbors and friends. I am lucky to be among them.