Prepare to be lectured.
You are exactly right, throughout history being armed has given the defender the confidence to stand-up to the criminal attacker. The low life unarmed criminals are generally cowards and lazy, they watch for easy targets. So the first sign of resistance they bolt. The statistics back this up and most won’t shoot someone if they are fleeing the scene. Be aware though of the young, dumb or drug crazed...and there is no real way to tell if they are this type of criminal...they may just do something crazy like retreat and attack, run and get a gun, or just come at you. By there very nature criminals are unpredictable and bent on evil, so warning them may result in retreat (whew good news) or may result in a more intense attack (oh crap)!
Now depending on the laws in your state and your own feelings/beliefs then you may want to tag them before they commit another crime against someone not so prepared like the elderly, children etc. etc.