Only Resorting to Sophistry

How does one prove to a victim of persecutory delusion that they would not harm her?

It is very simple. All one needs to prove… is that they have the sufficient strength to harm her and in any way that they fancied.

As a simple example, a chick might be adamant that you are an obsessed pervert and that you would turn into a sexual deviant the moment you have an opportunity, no matter how much of a gentleman you swear to be. Even if you are capable of controlling yourself while sharing the same bed, not even having any thoughts of doing anything nasty, the chick would definitely not believe you because her reason is clouded by her perception of you. She might even ask who was 'anything nasty' and how you would 'do' her.

What should one do under such circumstances?