Liberal guy and gal walking home from movie and are accosted by two large thugs one of whom barnadishes a large knife. They are robbed and the girlfriend is raped by the one not holding the knife at the guy's throayt. As it all ends, the girlfriend straightens her clothes and goes off with the thugs, leaving the liberal guy standing in his own piss.
Works every time; liberal guy buys a gun or two and starts sending rounds downrange at a loacl gunclub, learning how to defend himself.
It doesn’t need to take such a traumatic event. Almost every liberal is conservative in their core beliefs. By showing them this it can lead to a transformation.