Here are some points to ponder - If you are hidden from your attacker, racking the slide will make some noise and may give your position away.
Anyone seen the movie Desperado?
Antonio had to chamber a round in his Ruger 45 semi-auto behind the store counter without letting the bad guy know he was there (bad guy was standing in front of the counter). He was sweating bullets trying to quietly chamber a round - if he was discovered by making some noise - shoot out.
Why do we carry a loaded pistol(s)? We do it because carrying a loaded pistol is better then carrying a knife or your bare fists. Heck, some of us would carry a loaded carbine/rifle/shotgun if we could.
If you have the need to carry a pistol, you must think like a fighter who fights to WIN. I want as many variables of my combat situation (potential or actual) to my advantage. Having to rack my slide removes one advantage.
If you are in danger, you want ALL of your senses available to you so you can concentrate and quietly listen, look and plan your moves. What if your left hand has a flash light or some other object - you must make additional "movements" to rack your slide, losing valuable and critical time and focus.
I believe in training and practice. Try this out. Have your friend/wife/hubby rush you from the front door to the living room couch where you are sitting with your
empty gun holstered. See if you can draw and rack the slide then aim before your friend/wife/hubby stabs you in the chest with an imaginary knife. Better yet, shoot your head off with an imaginary shotgun from the door - See if you can roll on the floor trying to take cover while racking the slide. Anyone see the movie Mr. and Mrs. Smith? Even they had hard time racking the slides of their weapons and had to take cover to do so (love the movie BTW, it's a great training movie for my house)
Time is everything in a fight - I am not young and quick and full of you know what anymore. But I can still press a trigger
I love this quote: "God created men and Smith & Wesson made them equal"