Argumentative persuasive technologies are technologies that use argumentation in order to persuade the persuadee to believe in something or not, which can later lead the persuadee to perform an action or not. The use of such tools opens numerous ethical considerations. In this paper, we survey the literature on persuasion that might be useful for argumentative persuasive chatbots, we cover the existing legal framework and ethical principles and we critically analyze the new proposal for a regulation on artificial intelligence of the European Commission. We also show how to use argumentation to enhance explainability and transparency of the persuasion systems. We propose to show the graphical representation of the arguments used during the persuasion to the user at the end of the dialogue, containing the relations between the arguments (attacks, supports), their origin (source), who uttered them (i.e. the machine or the human participant) and the persuasive methods employed. Our approach has several benefits. Namely, it makes the system more transparent and enhances the human understanding of the system, which is a benefit per se. Furthermore, the fact that the system is transparent increases the trust of the user, which (apart from being one of the goals of AI in general) can increase the chance that the user is persuaded by the system. Finally, the user can give a feedback on the presented arguments (e.g. how much they believe the arguments are ethical), which can be later used to improve the persuasion system.