I would say during the hippie era. That was when pop culture began to look down upon the traditional man as an outdated, bigoted, racist warhawk. Of course with that, traditional masculine things like knowing how to fix your car when it broke down, or how to run a farm, or how to engineer systems were lumped in with the old world, since those were competitive and not the new age of "kumbaya we will all live together in our multiracial paradise".

Then came sitcoms where the man of the house was portrayed as a bumbling incompetent while the wife was portrayed as intelligent and responsible. You had shows before that like I Love Lucy where they had female characters, but they didn't put down the male ones. That changed with shows like the Simpsons or King of Queens.