The very reason of how words like "retard" evolve in the first place is by people using those words outside of the standard dictionary definition's meaning.

What I want to say is that just like there's a huge difference in meaning between "this is shit" and "this is the shit", even usually insulting words can be used in inoffensive ways(like it's done on WSB) - and of course the other way around you can call someone a "genius" and make it obvious you meant the exact opposite.

Language is an incredibly flexible tool and every dictionary definition or scientific description is an obsolete snapshot at best.