In the sexual harassment case, for example, in the absence of the threat, the recipient could choose between having sex with the intervener or not. But once the threat has been made what he or she can decide to have or not is coerced sex with the intervener, which is something quite different. In addition, the alternative of taking the job now involves working for someone who has treated one (or tried to treat one) in this way, and declining it can be seen as an assertion of one's dignity. More generally, whatever A may be, the threat to attach a penalty to the recipient's doing A changes the alternative of doing A into the alternative of doing A in defiance of this threat, and adds to B the character of giving in to the intervener and being "pushed around" by him or her. (p.39)
He adds on p.40, "Recipients may have good reason to object to changes of these kinds in the meaning of the actions available to them, and therefore good reason to object to others intervening in their lives in these ways."
This strikes me as an important point, but I don't think that the potential moral objections here depend upon the actual motives or intentions of the intervener. Rather, it seems that what matters is their apparent intention, or what the recipient could reasonably interpret their intention to be. For example, it may be that I have no intention to threaten you at all, but if I carelessly make a remark that is naturally interpreted as a threat, then that seems sufficient to problematically impact the way you perceive the meaning of your subsequent choice. Presumably, the im/permissibility of my causing this is unaffected by whether I did so intentionally or negligently. If I should have known better, then that suffices to settle the question of permissibility; my actual motives don't matter.