Dean Jones says:

"But I thought you had experience teaching all of the classes we need to offer in our department...Are you, or aren't you qualified to handle our teaching load? 

What is the saying?  'If you can't run with the big dogs, better stay on the porch!"

Your response:

1.  Of course I am qualified... and upon further reflection, I accept your kind and generous offer.

2.  Of course I am qualified.  For you to even insinuate that I am not qualified is, frankly, insulting.

3.  Of course I am qualified.  It is not a matter of qualifications, it is a matter of how to allocate my time between teaching, service, and research.