Store auditioning and then buying on-line from others. How do you feel about it ?

Doesn't look too pretty, but who cares, right ?

Another asked and answered thread.
Are you asking to hear answers or answering to hear confirmation?
To your first question, it falls somewhere between bad form and stealing, IMO.
To your second question, my answer is "wrong."
"Who cares" is an unfortunate opinion.

The whole B&M buying experience is in rough shape after being assaulted - first by the big box stores and later by internet sales.  As margins began to decline we started seeing lower paid, younger salespersons with less knowledge about the products.  The internet has not only resulted in many manufacturers selling direct, without the added cost of a dealer network, but it also offers a vast amount of information on just about any product.  An astute internet researcher can usually learn more about a product on-line than they would learn from a salesperson.  Also, B&M stores simply cannot carry the variety of different gear a buyer can consider when researching and purchasing equipment on-line.  The main advantage of a B&M store is the ability to hear products prior to purchasing but on-line dealers have largely overcome that advantage by offering in-home auditions and 30-day money-back options.

Some folks like the B&M experience and wouldn't consider purchasing high-end audio equipment on-line.  Many however have increased their knowledge about different gear because of the internet and are more comfortable purchasing gear on-line. My personal solution was to simply stop visiting B&M stereo shops.  One could argue that I may have actually made less mistakes and saved money had I continued to purchase my gear from B&M stores, where I could hear the gear first.  I am not sure that would have been as much fun, and I certainly wouldn't have been exposed to such a wide variety of different gear. 
Although nobody is "obligated" to support a dealer by purchasing products from a B&M store,  they should not abuse the hospitality of the B&M store by shopping there with no intention to purchase from the store.

I mean, these guys are looking at making $8,000 for a couple of hours of their time

Hardly. Consider the payroll spent on all the time required to order, stock, and display the gear, the time spent by salespersons standing around waiting for customers, dealing with tire-kicking customers who do not purchase, and helping with post-sale advice, set-up, and consulting.  Not to mention the cost of stock, discounts on items that do not sell, employee training, employee benefits, rent, cleaning, bookkeeping, etc. etc.  I would not want to be in that business.

is it so unreasonable that I ask the store manager not to be an idiot?

Not at all. Capitalism is all about voting with your wallet.  I wouldn't buy from an idiot and in America you don't have to either.