Publicity and self-promotion are as American as apple pie. I agree that it is a deplorable thing, but it is unfortunately with us. Now if you want to make an argument that it is unethical, I think the best way to do this is by focusing on in context. In other words, publicity is fine when the context calls for it and when people know that it is coming. This is fair or we can say it is ethical, because people know that they are being "sold" something.
Where it gets unethical is when people do not expect it or when the context does not call for it. Publicity and self-promotion at this point exploits people. For instance, if there are publicity attempts at a funeral where people are vulnerable, it is unethical. We can multiply contexts such as: school, places of worship, and the work place.
Also by juxtaposing things like advertisement and certain contexts, it is possible to create an illusion that a certain contexts endorse the publicity, which can be very false.
I guess I need more context to genuinely offer an answer here. On one hand, I don't think that publicity is unethical. In an increasingly competitive world where individuals seek to be known and where being known represents so much, publicity might be needed. In my mind and in its purest form, I don't see anything particularly unethical about self promotion and generating publicity for one's accomplishments. I am not sure that this violates the strict view of what ethics is and what it encompasses.
Where I think the issue gets complex is in the idea for publicity for simply being. An example would be the modern celebrity who generates publicity and self- promotion for simply being. It is not that I am against this, but I think that this is where publicity and self- promotion are not operating in the best interests of the social good. However, with that being said, publicity and self promotion only advance if there is an audience for it. If individuals are willing to patronize and pay attention to publicity and self- promotion, then it becomes relevant and continues to stay relevant. I am not sure if this is unethical because it is pandering to an audience. If there is an ethical good to be emphasized, it might be for individuals to not support campaigns of publicity and self- promotion for the sake of the celebrity. If individuals are able to stand for this, perhaps some type of moral or ethical stand could be made. Yet, in the end, if individuals sanction and support such behavior on the part of celebrities, it will continue as it helps to make them more relevant and meaningful to whatever discourse of which they wish to be a part.
I doubt that most people think that publicity is unethical. However, if you are required to argue that it is...
One can argue that publicity and promotion are unethical because they twist the truth. Publicists and promoters are, one can argue, not really trying to spread the truth. Rather, they are trying to get us to believe in a given point of view or buy a given product. Because of this, their business is inherently unethical.
However, this does not seem like a fair way to characterize these professions. Those of us who consume media already know that publicists and promoters are trying to put the best face on various things. We know that every point of view has the right to be heard and every product has the right to be promoted. So long as the publicists and promoters are not telling lies, it is up to us to understand that many of their claims will be hyperbolic.
In this way of looking at things, publicity and promotion are not unethical. They are an integral part of a society where various companies, politicians, and others compete to "sell" us their products or ideas.