Don't get me wrong I totally understand where you're coming from. Try to think of it this way. P2P software basically creates an overlay network. This virtual network only exists "within the software" therefore it you are not running "the software then you are not a part of this overlay network." If this specialized network doesn't exist without the software. Where is the distinction?
This is exactly the situation with ISPs who created walled version of the Internet i.e. AOL. or cable internet providers. They control a significant portion of the resources that make your communications possible. Therefore they are not only providing access they are providing a service.
http://news.com.com/2010-1027_3-1023...ml?tag=fd_nc_1