I value my privacy and find it silly that I have to log in. They offer no information as to why I must log in, I am just hit with a log in page. If this were under an NDA or something and it was an agreement into which I entered willingly, I would not be so opposed. As it is, they are simply farming my data and I don't like giving that up freely.
I think there is the growing problem that most people are increasingly willing to divulge their personal information, specifically online, and then have a backlash at anyone who doesn't feel comfortable doing so. It's trivial you say, just as it would be trivial for me to be forced to show identification whenever I get on a bus, but that doesn't mean I am going to be alright with doing so. Like the argument that only people who have anything to hide advocate for privacy. This example may sound a bit extreme but it is essentially the same argument.
Anyway, you're entitled to your own opinion, but I don't think it's going too far to be perturbed at giving up some of my privacy to look at an API.