GP is obviously aware of that way of using 'man'. That's why they're asking people to stop doing that.
Besides, a dictionary* simply describes the way we use words - those ways can change. Language is not set in stone.
You (like almost all SJWs out there) seem to misunderstand the meaning of "privilege".
"Privilege" is something given by a royal or government decree to some specific person or group. The normal state is "unprivileged", and "privileges" are to be eliminated by rational society.
Meanwhile, when speaking of sexism and racism, there is no "privilege", because the "unprivileged" state is not normal (and the whole society is not mean to be reduced to it). You might speak about "discrimination" or "oppression", but "privilege" seems to reverse the meaning.
* descriptivist, as most are