What a rubbish from the IOTA fanboys. Certainly it is not safe to post any private key online or use it to log into your wallet. That's why no wallet uses a private key to openly login, only the IOTA wallet does that. And as I wrote several times before, they do so without authorization.
Again, AAA: Authentication, Accounting and Authorization, the 3 pillars of information security. IOTA failed to implement authorization. And that's what they are to blame for!
This is a lie.
You are probably German, call everybody a liar, that does not fit into your small limited world. LOL