Difference of opinion I suppose but having a weapon doesn't make a game any less frightening.
First playthrough of Dead Space 1 for example. Horror Survival done right.
To me the inability to fight back, irrespective of how futile it may be, completely ruins the immersion. I am a grown man in real life so regardless of being frightened my natural instinct is to smash whatever frightened me. This game would not allow for that so a huge chunk of the experience is in fact missing.