+1 for overreacting. Swearing at somebody because they're curious about how you're doing something is a little much.
Most people are pretty reasonable, and if you'd told him you were working and would explain things in a few minutes, he probably would have backed off.
They're using your compositions because for the last 30 years or so, the world has been furiously teaching people that they don't have to think for themselves or make any real effort.
I'm amazed they were up and about at that time of day.