It's quite easy to grow weary of typical gunshop/gunshow antics (pseudo machismo types that we're all familiar with). However, one thing that I have yet to do in a legitimate gunshop is haggle on prices of accessories. I can't see myself ever doing the same at Wal-mart either; their shop, their prices.
The whole "arm on the shoulder" thing leads me to believe he either thought you two were chummier than he should have or has an arrogant demeanor. Either way, perhaps avoid the shop if you have other options.
For me, I don't chew the fat like most others when in a shop, so there's little mistaking that I don't want to get chummy with anyone. I request a price on something I'd like ordered, listen to their price, express interest or offer a simple "I'll pass, but thanks anyway". Perhaps on-line shopping has made me antisocial, but I'm never in a gun shop for more than 15 minutes....