You heard them moving through the house. Anytime someone is attempting to maneuver in stealth against you, you can guess that their intentions are bad. And you did just that, arming yourself with your Glock. The light you added made you feel safer operating in low light, and that article you read said that all gunfights happened in the dark. You kept both hands on the Glock, just like on the range, and it helped steady the pistol through the waves of adrenaline. Not wanting to shoot an innocent, you had turned the light on with your support hand as you began to move through the house and -
End of story - the bad guys saw your light and sent a magazine of ammunition your way. One of the thirty rounds hit you in the head and you died.
Let's try again shall we?
You heard them moving through the house. Anytime someone is attempting to maneuver in stealth against you, you can guess that their intentions are bad. And you did just that, arming yourself with your Glock. The light you added made you feel safer operating in low light, and that article you read said that all gunfights happened in the dark. You kept both hands on the Glock, just like on the range, and it helped steady the pistol through the waves of adrenaline. But as you collected family members, you had to let go of the pistol with your non-shooting hand to keep the little kids moving and safe. Then you saw a figure in the hallway. Was it a family member? You couldn't tell who it was, so with the firing hand trigger finger (your other hand occupied with your five year old) you pressed on the light button. Then you saw his face, snarling as he brought up his own pistol. And then -
End of story - the bad guy shot you in the face while you identified him as an adversary with your light. One of his thirty rounds hit you in the head and you died.
So let's have a short talk on how to use a light and just as important...why.
1). The need for illuminated target identification has been vastly overblown by light manufacturers and liability-centric instructors. The figure in your house that is not a member of your family...silhouted in the moonlight moving uninvited through your house is bought, paid for, and gift-wrapped. There is no need to identify him any further nor even to say a word before you press. If you have a problem with that you are placing the enemy's life above yours and that of your family. And that is a craven and foolish thing to do. Keep the light off and your mouth closed and press the trigger.
2). We can debate home defense weapon selection, but if you have non-combatants that you are responsible for such as children or elderly family members, you will need to grab them, carry them, or physically move them. In my opinion, this duty necessitates the use of the "one handed" gun over carbines and shotguns. And even if you are sufficiently strong to move through a house clearing and moving with a long gun in only one hand (you'd be surprised how many modern Americans cannot), you would still need to occasionally operate that light while conducting your duties.
3). It is imperative to be able to turn the light on and off while your finger is on the trigger. It is also imperative that the light is never in "constant on" unless you are working in conjunction with others. Absolutely required for fighting lights is a momentary on switch (not an constant on - constant off), and a remote switch that allows you to operate the light with the grip pressure of your shooting hand.
4). The light is used very, very sparingly. In tactics circles, when moving outdoors in a fire-and-maneuver context, or a movement from cover to cover context, the shooter is admonished to keep his exposure to a minimum. So, as he gets up from cover to move, as his partners apply suppressive fire, "I'm up - he sees me - I'm down". The idea is to limit exposure to a time interval of 3 to 5 seconds.
In the low light/darkness application of the weapon light, we do the same thing. We limit "light time" to short bursts of light, only when we need to visually see into a dark pocket, and only for a brief flash. Minimal light use keeps you safe and alive.
5). Yes, in the real world people get covered with gun muzzles all the time....ALL THE TIME. The idea that you are never going to cover anything with a gun muzzle is a gun range fairy tale. Get over that sort of thinking because aversion to point your pistol at a perceived threat gives that threat an advantage. Unless he is a total incompetent fool, he will take that advantage and kill you. Just because you point...even if you are touching the trigger...doesn't mean you are going to shoot. But when you illuminate someone that by all accounts is a threat to you life, you better be ready to kill him.
6). The weaponlight is NOT a reactive self defense tool or a necessity. If a bad guy jumps out at you in a dark parking lot and there is enough ambient light to see him, you can kill him lickety-split without even having a flashlight. I do not CCW a weaponlight on my pistol because I understand this dynamic. All my lights are reserved for proactive mission weapons.