To all those who believe they can "sufficiently/timely" rack the slide "if/when" an immediate threat to life situation occurs:
When I was a teenager growing up in Los Angeles, I took up martial arts training as a hobby for self defense. The instructor taught the "traditional" form first during each session and always followed with "practical/street" form by telling us, "When you are in a real fight, use the street form. Use the traditional form for formal matches and belt grading."
He told us he taught us "street" form because when he was younger, cocky and stupid, he often got into fights. Although he was proficient with the TKD techniques, when knives were pulled out he had to be more efficient with his form to buy him time so that he didn't get stabbed or sliced. We had many hands-on sessions where we learned to disarm attackers with sticks, knives and pistols.
After demonstrating several pistol disarm techniques where he closed the distance of 10-15 feet in a blink of an eye to knock the pistol out of hand, taking away the pistol or pointing the pistol back at the attacker, he pointed out that most semi-auto pistols will not fire if you grab the slide from the side and push back on the slide so the barrel is out of battery (he used a single hand twist motion with palm on frame and fingers on top of slide). When some of us "gun fans" asked what's the best defense against someone like him, he said to use a blocking arm out front, use a quick draw and shoot from the hip/chest BEFORE he gets to you because we'll have very little time to react before he is on top of us.
When I took my defensive training classes, we were trained that we often had less than a second to react/respond to an immediate threat. We practiced drawing and firing in one smooth motion from holster to center of chest with our weak hand out front as a shield/block from the attacker who might be close (Elbow pressed firm against the abdomen provides support for the shooting hand).
Many of us have never been in a "real fight" or been punched/kicked for real. When someone is planning an attack and executes the initial hit, they do it to make it count. Often, the target will have very little or no time to react. It all happens very quickly in a flash. If you are hit in any way, your ability to perform "typical" gun handling will be severely impaired. Only thing that will help is repetitious training so your response would be automatic and instinctive.
Here's a test. How many of you practice so you can reach, draw, rack the slide, aim and hit your target at 5-7 yards with your eyes closed? I regularly teach people to perform this task in under a second, BUT the pistol must be chambered.
I live in a city where crimes against individuals on the street and violent home invasion attacks occur on a daily basis. Believe me, I KNOW I am prey, not a predator. I think like a prey and take every advantage I can turn to my favor. If I can save a precious fraction of a second so I don't have to rack the slide, I will.