I have heard this from the anti gun crowd since I first started carrying a handgun.

Back many moons ago you could carry a handgun at age 18.

If you had a gun to protect yourself, but the crook could just take it from you, you wouldn’t need a gun. You could just take the crook’s gun and use that.

Source: Helpless-Victim Myth “If I Had A Gun A Crook Would Just Take It”