Bullying is a behavior. Behaviors are learned. They do it because it works. If you want to make it stop – you have to make it stop working.
The answer to the question – does it help to ignore a bully – is complicated. It depends on what you mean by – ignore.
In my opinion – the psychological abuse of a person for the benefit of the perpetrator. – should be illegal. It only is illegal in a few places.
Parents, if you were never taught how exactly to get a bully to stop, please learn it. There is a science to it. Yes, an actual science. It’s called behavioral psychology and there is 70+ years of research into the subject.