::::::A public medium of communication can be anything. A roadside sign falls into this category. "A means of mass communication, such as newspapers, magazines, radio, or television" is not limited to those mediums, "such as" is the key here. "I spent most of my career in advertising" isn't convincing. Your opinion is based on your own experience in your own field, but that does not necessarily mean that your interpretation of advertising is supported by the wider community. Regarding "you don't know what you're talking about", please, be civil. Attacking the integrity of other editors is not affording respect.