Married Priests?

This article from the Milwaukee Journal/Sentinel Website talks about the Archdiocese of Milwaukee getting it's first Married Priest. http://www.jsonline.com/story/index.aspx?id=776571 I read the article and find it disturbing.  Why is ok for someone who is a married Minister in another faith to decide to convert to Catholicism and they can be ordained as a priest but that anyone is Catholic already can only become a priest if they decide to pursue that avenue before getting married?  Even Deacons can only be married if they were married before they became a Deacon. Let me clarify my point here.  I don't have a problem with this married priest coming to our diocese.  I think that the entire restriction from having married priests is wrong.  In the article they explain how this is allowed and in it they quote Pope Paul as saying that celibacy is not required by the nature of the priesthood.  It is a redical sign of commitment but it is not essential.  So if one Pope in the past has said that it is not a requirement then why is the Catholic Church so against allowing this when it would probably help our priest shortage around the world?