P channel FET reverse polarity protection - toggle switch on base
The Source and the Drain are swapped, so the MOSFET reverse diode is always conducting.

Also, you put a switch at the GATE, not at the base which a Mosfet doesn't have.

EDIT: For polarity protection that is the way to connect but then you cannot expect to turn the FET off since the reverse diode will always conduct. If you want both polarity protection and switching you need two back to back MOSFETs