Your point would have been valid if it were simply being courteous of a sales professional's time and thinking about whether or not you're taking away business from him, but you and the other guy went overboard by calling it "theft of service", or comparing it to software piracy. It's not theft at all.
Is it wrong to go to five car dealerships and test drive their top of line cars when you have no intention of buying? It's certainly not a very nice thing to do, but along with tying "up a sellsperson for up to an hour" with no intention of buying, these are extreme examples. It sounds like you need to get some new friends; I certainly don't know anyone who would do such a thing. But I don't call them thieves or insinuate that "you are stealing from that store as if you pocketed something and walked out." That's insane, and simply incorrect.
I buy from brick and mortar stores on big purchases because the value proposition is better. The online price might be cheaper, but shipping costs usually equal out, and I prefer the convenience, return policy, and warranties at the physical retailers. However, I don't think it gives me any moral or ethical high ground.
To people like you, what really goes on in the sales process might be a lot like seeing sausage made.
I racked up $700 in expenses in one night during a trade show taking a prospect and her assistants to drinks, dinner, and a show. I had clearance to offer her a better price against a competitor who offered a parallel service. I found out later that she was shopping for a better offer simply to take back to my competitor as leverage to get them to lower their cost too. She had no intention of going with my company from the get go. Was she "stealing" from me, or guilty of "theft of service" because I advised her on the different tools and bought them a boatload of hospitality that night? No, of course not. It's all part of the game.
Abortion is legal. Does that make it ethical?