This might seem a little trivial but but it is a serious question.
Here's the scenario:
You're the head of a department but you don't like the way a member of staff speaks to another member of staff. You put up with the nonsense for a few days until you decide enough is enough. You ask that staff member to stop speaking that way as you sound like a bully. That person doesn't like being told what to do. As the head you tell that person "you will not speak to me the same way as you do to him/her". That person then says "come on then!" where you both storm to a room. The head gives that person the opportunity to take his shot. He then walks out only to tell the head a few days later when things seem to have calmed down the he or she is unprofessional and aggressive!
What is your interpretation of "Come on then"? I know what it means in England.