I was accused by a baker of lacking human decency cos
a) I was too busy to answer and return calls
b) I addressed him in the 'cc' rather than 'to' of an email, which made him think he was an after-thought

But whatever guilt he could've induced in me (yes I'm a softie) vanished when he told me I treated him like a delivery boy.
"How?" I asked.
"You emailed me to do something without even saying please," he replied.

And I got up immediately to walk him to my terminal to check that responsible email. Not only did I write "please", I wrote "thanks" too.

Moral of the story: You have to be careful not to accuse people of characteristics not inherent in them. I never not thank people.