Flashlights are a tool we have all used, likely since we were kids. We have used them to navigate and do administrative tasks for a long time. And using them with a firearm seems like it would just be adding what you know to the gun. But what if we could be more effective?
Using a flashlight in a defensive context is not necessarily the same techniques we would use in an administrative capacity. For instance, when we use a light to see things without defense in the works, we do not care where the flashlight is located in relation to the body. In a defensive context, we want to keep the visible target (all the threat can see is the light, right?) away from the body so the potential incoming rounds are not directed at our body.
In addition, we can use our flashlight for misdirection. If we are shining the light one way, can we still see something in another direction? We don't necessarily need to telegraph the direction out eyes are pointed by looking only the way the light is shining.
And how about weapon mounted lights? They offer you the ability to use both hands to operate the gun, but you have less ability to misdirect and where the light goes, so does a muzzle.
Does this mean you shouldn't have a flashlight? By no means! Understanding the light is a very important skill, and it should be taken seriously. Chuck Haggard, Ken Good, Thunder Ranch, Gunsite, and Mike Panone all offer great instruction on how to use a flashlight effectively IN A DEFENSIVE CONTEXT. Train well, and understand your tools.