The pro-IP argument from Apple's point of view goes something like this:

In a world where everyone just copies everyone else freely (e.g. the desktop PC world) there is/would be much less innovation.

The investments that go into many breakthrough products (iphone, ipad) are made with the understanding that IP protections are in place to prevent copycats from waltzing in and taking all the benefits later on.

Take away those protections and the initial investments aren't made in many cases and the customer sees far fewer breakthrough products.