brush guards are never meant to be replacements for real bumpers.
you have to realize that the mount point (pivot point) for brush guards are under the radiator and to the front frame and not directly behind like the front bumpers. so of course in a frontal hit the brush guard is going to pivot at the mount point and whack the grille/hood/quarter panels.
brush guards are hardly used for the original intent for what there are. mostly they are used to make the other person think twice about backing into you in a parking lot.
but they do look nice. good example is my wife, she hated having a brush guard on her trucks, and on her latest 02 tacoma, i finally convinced her to put one on, and now she thinks it looks better with it on.
and yeah i have seen more often than not that brush guards cause more damager than if it was left off. but it dont matter, i have a $100 comp/coll deductible for both vehicles. easy up here since i only pay like $700-$800 for 100/300/100 full coverage for both trucks.