While I somewhat agree about the tracking (if every device gets a /64, then, while the device can chose the host part, the network part is fixed, so site owners would just track the network part to uniquely identify a device or subscriber), I don't see the argument about illegal contents.
To track a downloader of illegal content, you'd still have to go through the users provider and the provider can easily determine who actually downloaded that content at a time.
So as long as providers cooperate, it's not easier or harder to track down a pirate with IPv6 than it was with IPv4
There are currently several schemes for obtaining a full /128 address from a /64. One appends your device's MAC address and some other stuff to the network prefix. This obviously has some privacy implications.
The second appends a random number to the /64. This was added specifically to address the privacy concerns of the previous scheme, and does so as well as any easily routable scheme can. While it's obvious under this scheme what network traffic is headed to, it isn't easy to determine which device on that network is going to receive that traffic. Or that device's past network history, if it routinely switches IP addresses.
A /64 isn't a person any more than a IPv4 address is a person. It could identify you on your wifi, your phone, your friends phone, your friends laptop, the kind lady downstairs who you lent your wifi password... all it specifies is the destination subnet for communication.
If you're the least bit privacy aware, it's not any easier to track your device using IPv6 vs IPv4.
edit: IPv6 is arguably harder to track, because autoconfiguration proceeds without a central DHCP server. In order to log IP <=> client mappings, a router would need to listen for all Neighbor Solicitations to outgoing devices, not just add a couple printfs to the DHCP server.
Honestly, I can't help but hate you when your first thought with "privacy issues" is illegal downloads. Even if you thought that was the main reason for 'net privacy, why would you say it?
To track a downloader of illegal content, you'd still have to go through the users provider and the provider can easily determine who actually downloaded that content at a time.
So as long as providers cooperate, it's not easier or harder to track down a pirate with IPv6 than it was with IPv4