In summary: I don't necessarily think it is offensive to say that bugs are coded by developers, because they are. However, it is offensive to say that they are responsible for the bugs without taking into account the broader context in which they are working (and indeed, saying they are responsible for the bugs still doesn't necessarily mean that they are in some way wrong or deficient for entering a bug. People - even brilliant people - can and do make mistakes, and that is why review processes do (or should) exist.
Yes, that's a good way to put it. I wonder if they considered attaching biometric probes to managers to find out when they are most likely to come up with stupid ideas?