OP, what did you hope to learn from starting this thread and is that any different to what you have learnt from it?
You've said that your kids haven't been bullied, so you don't know that gut wrenching sickness when you stand at the school gate in the morning knowing that your child or teenager or whatever is going to suffer in there, all day, and the day after, and the day after that and that the adults meant to be helping them are saying "well, you know, its not all black and white ..."
Its a bit of a pointless expression, of course not everything is clear cut, I think its quite insulting to say that people whose kids are bullied THINK everything is clear! But I have to say that people that normally feel the need to use that expression, often school staff, rather than just being inclined to state the obvious, also feel that to be bullied somehow means your character is flawed, that those who are not bullied are in some way "better" - for example, bullied kids take up lots of time and effort, their parents often come into the school and want to talk - all stuff that teachers would rather not deal with.
My DD is nearly 17 and she left the school where she was bullied 2 and a half years ago - the sight of any of the girls involved in the street still makes her sick with fear and worry, she says she hates herself for feeling like that. I don't really have any time or sympathy for adults who want to talk about things not being black and white. Yeah, ok then. 