Obviously, there are lots of trackers out there. But the fact that those trackers exist, and we're sorta, kinda, maybe ok with it, or at least resigned to it--that doesn't imply that we're ok with any third party using leaks of that information to track us.
Probably the reasonable thing to do is say "if we're ok with X tracking us, we're ok with everyone tracking us, because the information will leak." But that's not the same as saying it's ok for everyone to try and make it leak.
It wouldn't at all surprise me if it's against LinkedIn's TOS, and the author admits as much.
What about this is not unethical?