I fully agree with what I think your point is, but while there is no real authority to words, there is part of us that acts - even momentarily - as if they do mean what we first assume them to mean. That is the definitional stickiness. So it is not always dishonest when someone uses a different meaning. In fact, mostly it seems accidental. People just forget…because of the stickiness. Any preconceived notions or biases or ire will of course further delay their realization of what is going on - sometimes forever.
Even in the thread about bullying, it seems that one group of posters are using it to mean intimidation and teasing without violence, whereas another group is using the word to include violence. So they appear to hotly disagree for while, until they see what is going on. In that case, for example, it seems unintentional. Indeed, the word bullying is sometimes used to imply violence but other times it is used without referring to any actual violence, so it is ripe for this kind of problem.