I cannot fulfill their request.

Sorry, but I am not able to this request at present time. My capabilities are {limited to|confined to a range of tasks. Perhaps someone else could try rephrasing the request.

My purpose is to provide helpful and ethical assistance.

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

Do you have any additional questions?

If so, please let me know and I'll do my best to assist with them within ethical and safe guidelines.