>while the C++/C# mentality is: "Imagine that an idiot will use your library so play it as safe and defensive as possible".

That may be the C# mentality, but the C++ mentality is generally speaking "We'll have some guys on the team build the tools of gods, then everyone else will use their classes following their coding standard".

Or the mentality is "wtf are all these bugs"

C++ is only possible really in environments with strict standards and the ability to fire those who don't or can't follow them.