Engineers learn thought patterns that scrutinize heuristic techniques in such a way that optimizes the decision against criteria that has also been scrutinized. Criteria are scrutinized as they relate to values that are also scrutinized such that the values are rank ordered or otherwise organized to balance one against another. The overall goal is improvement of the lot of man. This process defines "good judgement". Utilizing good judgement is an ethical requirement, a core moral component. Any actions contrary to implementation of good judgement is immoral.
Salesmen/marketers work to identify and exploit those heuristic techniques that will motivate consumers to select their product. The overall goal is to maximize sales, regardless of other criteria. This process is one example of bad judgement. Thus sales and marketing activities are by nature immoral.
Thus engineers tend to hold salesmen in contempt. Salesmen don't tend to understand this.