Ziggy, the psyche of a violent attacker is different from yours or mine. These guys understand fear and how to create fear in their prey. Attempting to intimidate a really mean SOB by racking a slide is, to them, just a challenge. If you REALLY meant business, you'd already be in stance, aiming the weapon center of mass and taking up the trigger slack.
And maybe, just maybe, they won't play according to the rules you want them to. Maybe they'll start running at you as soon as you pull the gun, and by the time the slide is getting racked, it will be taken from you, or a fist the size of a watermelon will be slamming into your head.
It sounds to you like you fear your weapon, or you don't have the confidence to carry with a round in the chamber. Practice carrying and drawing, become familiar enough with your weapon that you no longer fear a negligent discharge. Get snap caps for your practice. And here's one - have a friend stand 20 feet away and start running at you at the same time you draw (USE SNAPS CAPS). Can you rack the slide and pull the trigger before they reach you? 10 bucks says you can't.
Actions meant as psychological deterrents, even ones that seem very frightening to you, will often have NO EFFECT AT ALL on a really mean SOB. In the fantasy of their mind, they are 8 feet tall and bulletproof, and you are making hilarious, empty threats. Don't prove them right.
If an attacker believes you to be unarmed, you have more of a tactical advantage. If you wave around your pistol, they can get used to the idea of you being armed, and overcome any fear they have.
Sorry for being long-winded.
ishi
That brings me to a question for the experienced gun guys: do you not see any possible value in the act of chambering a round being, in itself, a major deterrent to the BG in continuing whatever it is he's doing?