I know every situation is different.
The one time when people entered my home illegally, in the middle of the night (3 am actually). The first thing I did was get my shotgun. The second thing I did was turn on the hallway light.
Why turn on the light? I could have just shot them in the dark, right? There were two other people living with me and I wanted to know for sure that I was pointing that 12 gauge at the uninvited guests and not one of my roommates.
I challenge anyone in the "shoot them in the dark" side of this argument to show me two reputable defensive shooting schools that advocates against the use of tactical lights.