Welcome to the Apple Community.
Why should you be angry, most people already have one of these leads, they come with most digital cameras and other similar devices. Had one of been available in the box, you would have paid for it whether you need it or not, assuming you now need to purchase one, you will now only be paying for something you would have done anyway.
Unlike "most people," I don't have the micro-USB cable. My digital camera has a cable, but not one that would fit into the end of the Apple TV unit. When I bought the unit I did not need the cable, not having foreseen that Apple would jam an "upgrade" down my throat, said upgrade turning my unit into a paperweight.