Demonizing is not to be found in the field of propaganda, but rather in that of information, insofar as it is based on fake data and parted in an overall plan. It is practiced all the time, of course, but the simple fact that the expression spontaneously appeared in the written and spoken language indicates that it has begun to be used more systematically, since it suddenly feels the need to define it. It simply means telling as many evil things as possible about the potential enemy, often in an absolute, but based on the means of misinformation - false information, false statements, false photographs.
In Advertising, Demonizing is not practiced openly. Denigrating a competitor's product would risk drawing attention to it.
Misinformation almost always seeks to create two camps, the good and the bad ones.
Public opinion is like a big child, and it works pretty much the same way, with the help of a soulmate: the misinformer.