Germans are awesome

So I was in Kaufland to-day, and Thomas and I were thinking about going swimming. He asked an employee: "Habt ihr Swimmbrillen?" The employee responded "Haben Sie Schwimmbrillen. Nein."

You see, Thomas had used the informal form of the plural "you," rather than the formal (which he later explained was generally inoffensive in the specific context of asking a store employee about the availability of wares). The employee, without even stopping to consider things, elected to take him down a peg before answering his question in the negative. I couldn't stop laughing. This behaviour was just so foreign to me.

Am I right in thinking that this sort of behaviour would get any employee of an American store in trouble?