Using a local business as a showroom for an online business is unsustainable. If enough people do it, then the local business will cease to exist.
It's perfectly legal, and I don't particularly think it should be made illegal, but that doesn't make it ethical.
The local merchant has the advantage, but many of the small, local merchants around here seem to be content to pull a Leon Lett on the 1 yard line. [0]
"Sorry, our price is $XYZ [50% higher] and we don't price match."
"OK, fair enough. <tap, tap, tap>"
On the flip-side, Home Depot, BestBuy, and Target have generally competitive pricing to start and do price match online competitors, so they get a lot of my "need it now" business.
Either take the gamble and order online sight-unseen, or pay the higher price involved in maintaining floor space and inventory.
Is it impolite to bust out a phone right in front of a sales rep and say "hold on, let me check amazon", sure. But there's no moral responsibility on the customer's part to do business with anyone because "hey man, it's more expensive for me to run this business".
This isn't some surprise to retail. This has been going on for over a decade. You can't compete with the internet on price for (many) things. But you can compete on immediate availability, customer experience, etc. If you're fighting a price fight with the internet, gtfo of retail.
As I said, it's unethical to use a store as a showroom and then buy elsewhere. It's a simple concept, and I believe you're being intentionally obtuse and disingenuous in your reply.
Yes, this is inconvenient for the people who own those stores. No, the consumer isn't doing anything unethical.
But if people continue to behave the way that you're suggesting is okay, we'll end up with very few brick and mortar options and we'll have to rely entirely on sight-unseen information in our purchasing decisions.
Some stores are made to browse, and it's less of a problem to come in and not buy, but it's still a problem to explicitly come to browse to buy elsewhere.