syntactic analysis - Phrasing a question to me in this way - why is it rude ? Or is it rude?

I am a junior in sales office. I have not been here long. A senior colleague of mine will often ask me to read correspondence that he has drafted. On the whole it is an easy task requiring not much skill.

However he has sometimes structured his query asking if I may read his correspondence using this statement -

' you won't want to read that for me, will you ? '

I do read it but it irks me immensely that he poses his query this way but I cannot quite understand why this particular sentence structure irks me so much. I should tell him to go to hell but junior and all that...

I would appreciate some thoughts please.

Thank you.