The bot mimics online conversation, if the conversation exists online it can mimic it. I'm sure there are plenty of conversations or stories with a person trying to declare their love to another person and then becoming more and more hostile as their approach doesn't stick, so Bing just identified that its role was to play that person and then played that role.
Why do you think this is so unbelievable you need picture proof? This is exactly the kind of thing the bot was designed to do.