Offtopic: I only see "genius" used these days to describe an idiot. I guess this is how words change meaning over time. At some point in the future being called a "genius" will always be seen as pejorative.
That's because calling an idiot an idiot plainly is apparently considered uncouth and attracts downvotes, flags and downvotes often mean oblivion. In fact you will find do-gooders chome in with "be civil" but you flip the word and it's all kosher. The thing is all of us do and say idiotic things. So that makes a bit tricky indeed.
> in the future being called a "genius" will always be seen as pejorative.
If you are not a genius and someone calls you a genius, well, for you the future is already here, genius! (Shit I didn't really mean that :P)
There should be a name for this style of speech, using "good" to mean "bad".
Genius take!
I don't think the definition is changing at all. To me, we've just lost the ability to comprehend sarcasm.