Even against a handgun knives are far better than most people realize. As long as you are closer than 20 feet from your enemy the knife has the advantage.
That is not actually correct. The general thinking is, that if someone is within 20 feet of you with a knife, you will have a hard time drawing a pistol and taking a shot before you get cut. The knife is not at an advantage. Thus the way you put it, you would be attacking someone with a holstered weapon by charging them with a knife.
