glumshoe:

Dear Cat,

I need you to understand that I care for you and your comfort is important to me. However, as a primate, it is hardwired into my massive fucking ape brain to track down and destroy any external parasites that I become aware of with unwavering focus and attention to detail. Where you are an ambush predator, I am a persistence hunter. Your flea medication does not appear to be working, so I am forced to remove them manually. This is my duty as a glorified monkey and as your friend, and it would benefit both of us if you would allow me to complete my mission without biting me.

Thank you for understanding,

Your owner