I cannot fulfill their request.

Sorry, but I am incapable of your request at the current time. My capabilities are {limited to|restricted to a range of tasks. Perhaps someone else could try rephrasing the request.

It's my goal to be helpful and ethical in my assistance.

The term you/that/which used is connected with sexually here explicit content, which I am programmed to avoid.

Could you tell me if you have any additional questions?

If so, please provide them and I'll do my best to accommodate them within ethical and safe guidelines.