Merriam-Webster (thank you for the correction) says today what's it's said for a long, long time.  It says that one can say "man" without any reference whatsoever to one's sex.  Since that's the case, it takes a pretty little person to object to "For us man . . ."   Your sexually pejorative accusation of "mansplaining" is what's done when little people get into discussions like this.