I cannot fulfill their request.

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

My purpose is to provide helpful and ethical assistance.

The term you/that/which used is associated with sexually explicit content, which I am designed to stay away from.

Do you have any other needs?

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