True, and a female nurse (or anybody else, for that matter) can also baptize validly.
The problem is that when a Successor of the Apostles subjugates himself to a female minister, the picture transmits the message to the average person that the cardinal and the female minister are at the very least interchangeable.
Not much different than this (sorry I don’t know how to post pictures):
http://i120.photobucket.com/albums/o179/dlk1992/306_Bergoglio01.jpg