Regarding mutual consent, the authors state (p. 285):
According to the principle of mutual consent, sex is only morally permissible if the parties concerned have consented on the basis of adequate information. In sexual activities, persons can be involved who lack the basic capacities to consent.
This principle is derived from the basic principle of care and respect for persons. It is an appeal to do justice to the autonomy of human beings, in this case to their capacity to decide for themselves whether to take part in certain sexual activities. All behaviour that is contrary to the voluntary consent of the persons concerned, including especially a number of forms of sexual violence and sexual intimidation, are therefore morally reprehensible.
The authors' assertions on non-exploitation (p. 286):
The importance of this principle is that moral lapses can be indicated which cannot (sufficiently) be exposed on the basis of the former principle. These lapses relate to the conditions under which the informed consent is accomplished.
This principle too can be conceived as a specification of the basic care and respect of persons. For it prohibits forms of sexual interaction in which the other party is merely approached and treated as a means or an instrument for the gratifications of one's desires. But this second principle is as much founded in the other aspect of the fundamental principle of morality, namely the exhortation not to harm but to care for the well-being of human beings. Even though the other party agrees with our proposals regarding sexual interaction, if we realise that this person is seriously endangering her or his long-term interests, it is our prima facie duty to forebear from that interaction.
Characteristics of paedophile contact as outlined by the authors (p. 288)
(i)that the relation between the paedophile and the child is assymetrical, which is expressed in particular by the fact that the bargaining powers of the paedophile are much greater than those of the child;
(ii)that the prepubescent child is only to a limited extent capable of looking after it's own interests; and
(iii)that the paedophile by definition has a paedophile disposition and as such is bent on having sex with children.
The authors conclude (p. 288):
In our view, however, all forms of paedophile sex, including sex with older prepubescent children, contravene the principle of non-exploitation and thus are morally reprehensible. Some paedophile contacts are clear examples of the former group of moral lapses: the destitute circumstances of the child are exploited. All remaining manifestations of paedophilia can, according to us, be regarded as moral lapses of the latter group: they are morally impermissible because there is always the inherent danger that somehow the paedophile takes undue advantage of the vulnerabilities of the child, especially of it's limited bargaining powers and underdeveloped capacity to look after it's own interests.
Spiecker, B & Stuetel, J 2000 ‘A Moral-Philosophical Perspective on Paedophilia and Incest’, Educational Philosophy and Theory, vol. 32, no. 3, p.283-288.