You are humming a song and minding your own darn business when someone else listens to your humming and feels compelled to hum along - in the wrong key. I am (sort of) OK with that. Look, there are several things wrong in this world and a tuneless hum is far from being the worst thing.
But when the shameless hum-hijacker listens to a few notes of your humming and confidently launches into a different song?
I am sure if we all looked hard enough we would find the Good Book allows an occasional murder or two.