I don't understand the outrage. Even knowing the context, the email is polite, to the point, tells the website administrator exactly what they need to do (something they are already legally required to do), and gives them ample time to do so.
I’m not legally required to reply in any way, although the email strongly implied that I am. This looked a lot like the kind of emails you’d get from someone gathering information before they decide whether to file a lawsuit against you.
