Difference between Set the cat among the pigeons and Set the fox to keep the geese

set the cat among the pigeons —(also: put the cat among the pigeons) do or say smth. that is bound to cause trouble and make people angry:

• Once again she set the cat among the pigeons, claiming that Michel was lying.

set the fox to keep the geese —(also: let the fox guard the henhouse) trust a person with smth. that he is especially likely to misappropriate or abuse:

• The committee made Hutton treasurer, that’s setting the fox to keep the geese.