Let's face facts - virtually no-one has an opinion of their own on anything. Knowledge, like virtually everything else in human culture, is social, and opinions spread like viruses, through contagion. Ideas are only real things when they seize the masses - and there's no moral difference between a good idea you thought up and one which you pull out of the mediasphere.
The idea of "originality", that people who originate ideas or memes, is an artefact of capitalism, based in the institutions of copyright and intellectual property. A lot of the soul-deadening nature of modern culture can be traced back to the fact that we only award people who come up with ideas for which property rights can be established, promptly alienated, and trades. In another culture, artists, memeticians, writers, politicians etc. might be honoured for the way they channel the "loa" of our culture into new product which enrich us all, but we might not be so hung up about the idea of "individual genius", which appears to just ruin everything.
You do not have an autonomous mind - you are an expression of the totality of human culture, especially in this cosmopolitan intarwebz era. Therefore, the question of the morality of marketing, propaganda, language-based thought control, call it what they will, cannot be boiled down to the question of "messing with someone's head" - we all do that, in a way, every day. There is only one human cultural mind which our individual consciousness refract in different ways. So, the question of the morality of marketing is a question of to what greater social end the meme is being spread (whether for the continued rise of collective consciousness, or to keep people ignorant so the savvy can profit from them); as well as whether the techniques used foster or retard trust and social cohesion, on balance.
The question of whether we should use deception and manipulation is, when you come right down to it, the question of whether we should use violence. The answer is: yes, in the right place, and at the right time, and only if we are willing to be fully accountable for the consequences of our actions. Swearing off marketing is the memetic equivalent of pacifism. Noble, but perhaps not sustainable in the world-as-is.
I realise I've just written off the existence of what might be called the "Higher" or "God" self in many mystical traditions. Well, good - every man and woman might be a star, but stars obey the laws of gravity etc. All that really exist in the "astral realms" are currents in the culture-sphere - we collectively make all these currents, but individually we are powerless against them. A "meme" is, in a way, a decision to all swim in a particular direction, which creates a new current, bolsters an existing one, or negates one we don't like.
