The problem with a bullbar, is the same as a bush gaurd. If you are going slow enough, sure it'll help some but if you cross the speed threshold, a potentially minor fender bender can be serious because the bull bar is now pushed into your radiator/engine internals. Also anything in it's path (grill, headlights, etc.) will be taken out.
I'm not sure the bullbar posted is for anything more than looks.
The only way to really protect yourself in the scenarios described is to completely replace the bumper (like an ARB or Shockworks bumper). Normal truck accessories aren't meant to run into things, and the accessories that are (off road steel bumpers/sliders) aren't cheap because they work. Most people don't plan on running into things on a regular basis.
