If you were driving along the public road on a car, you can't object to
people taking a picture of you, or taking notes about what you were
wearing, number plate, etc. You effectively loose the right of privacy
in public.
Etc etc
In my humble opinion this argument is completely bogus. The PSTN is a public network, but if I make a call to my grandfather in England, I don't expect anyone to be able to listen to what I'm saying without a warrant. If I have a unicast HTTP session, the content of that session is between me and the webserver. No-one should be able to look at that without a warrant.
Looking at IP/layer 4 headers is ok because you're not seeing the "communication content" and there is no personally identifiable information except your IP address. To correlate an IP address with me is something only my ISP can do, so releasing the info to a third party seems ok...as long as they can't correlate the IP address to a name/person.
Jonathan