True. But, a well lit target is not exclusive to the weapon mounted light (within the home). Not that Im against weapon mounted lights, but Im willing to bet that people were able to effectively defend their lives/homes long before such lighting systems became vogue.
Sure they did and to a greater extent with the advancement in technology that improves this ability. People got down the road in Model T's as well. You still can today...but.
Using a weapon mounted light can be a good thing, but it does require practice and forethought. Simply having it on the weapon is not enough. If using it "properly," you will turn the light on only as long as necessary...then turn it right back off (all via a remote switch). Otherwise, you are painting yourself as a target. In addition, given that the light is mounted on the weapon, when you have the light trained on someone you are also pointing a loaded weapon at this individual. To go one further, if you are easily "surprised" by what is "caught in the light," you may instictively be prone to firing the weapon. Not a good thing.
If you are surprised by what you see and instinctively fire the weapon, having a light won't make any difference. Training says "Keep your finger off the trigger". It gives you that second to think for one. If anything, the lack of light makes things questionable. Is it a family member? The Dog? A light takes a great deal of that away and this is where training comes in. One advantage the light has is the blinding effect it has on your target, especially an LED model like a G2 or Streamlight Polytac or TLR-1. Does it paint you as a target? Only generally and only if he can see you, which he can't. It paints him a lot more clearly and he'll be more likely to shade or avert his eyes or turn away than try to look at that light. The light can be a great "less then leathal" weapon because you can't hit what you can't see. Can he still shoot blindly? Sure, but it's all about giving you an advantage and the precious seconds you need before the 911 clean up crew arrives