I wonder what the hell you have to tell the police in Germany to take someone away for questioning (handcuffed, no less) based on an anonymous accusation. If I understand it correctly they didn't even search his home, at least not thoroughly.
From the link's comments, someone thought: "The police (no matter the country involved here) went way over the top on this. An anonymous e-mail is nowhere near enough evidence to go arresting/detaining someone without a thorough investigation first. The only possible exceptions being domestic violence, child abuse or a homicide in progress."