Where do we get the idea that women shouldn’t be in public office?
Some say the Bible. How about Protestant legend John Knox’s interpretation of the bible, to oppose a catholic queen? Just take a look at his The First Blast of the Trumpet Against the Monstrous Regiment of Women.
From this position, added to the fact that John Knox knew of Protestant preachers executed at the hands of Mary I (so much for a more peaceful world if women reigned, yes?), it was a matter of life and death for John Knox to oppose Queen Mary.