When it comes to understanding what someone is actually saying, what matters is what it means to that person. When it comes to arguments about etymology - eg whether "man" should be read as being about gender or species in a particular word or phrase, the history of the word becomes relevant.

So it's helpful to recognise that sometimes when some perople say "bad", they mean "good". But when it comes to deciding which sense of the word should be the default meaning, so to speak, the older meaning comes into its own.