Rude people

What is it with people? I was walking my Jerry Lee and he is a friendly if somewhat aloof German Shepherd dog and basically ignores people as he is much more interested in the smells that are all around. We had just passed the local shop when this couple were walking towards us and the women said something to the man who then very aggressively said to me "That dog should be on a lead!"
Rather taken aback I replied. "I beg your pardon?"
To which he still aggressive repeated. "That dog should be on a lead."
As I could not think of a smart, witty or cutting reply I lamely answered "So what?"
Which triggered a snarling unintelligible answer as he passed by me.
Totally puzzled I just said. "He want hurt you."
Grouche's reply was lost as he and the women, who had not said a word, went into the shop.
I was dumbfounded who was that guy and why was he so unpleasant and rude to me, I had never seen him before.
As for my Jerry Lee at no stage was he even close to the couple let alone looking in their direction as a nearby wall had very interesting smells on it and had his complete and utter attention for a fair while. So he is a GSD they are nothing to be afraid of. It is a fact that those lovely dovely labradors bite more people than any other breed of dog whilst the GSD is well down the list.
Even though those dorks were concerned they had eyes so why couldn't they see Jerry Lee was walking away from them as he was more interested in the exciting scents on the wall.
Yes it bugs the hell out of me. No need for unpleasant behaviour to a total stranger.
There will come a time when they will have to account for their actions - not to me - but to a higher source and I wonder what his answer will be.