It may be a difference between US and UK. To get someone's attention you might say Mister with neutral overtones, but more often we would call out, "Sir," rather than "Hey, Mister," which belongs to working class characters in 30s to 50s movies. If Mister is followed by a sentence, particularly an admonishment as here, it is definitely a bit abrasive. In New York we take it in stride from token vendors and taxi drivers, but a "well spoken." civil, educated person would say "Sir," even in a veiled reproof, as in "Sir, I think you dropped this wad of paper on the sidewalk."
I think that's probably right, Ktkee. The American fiction is that there are no social inferiors or superiors, so everyone is "Sir." A clerk in a clothing store would address me as "Sir," of course, but when also when I need his attention, I might say," Excuse me, Sir." Policemen who have had their training in community relations will arouse a drunken vagrant with, "Sir, you cannot sleep on the sidewalk." The flipside is that many feel free to abandon politeness when moved and drop the "sir." Once in a second-hand furniture shop in New York, when I started to bargain for a piece, the owner cut me off with, "Mister, gedaddaheah!"