I haven't seen a tactical or weaponlight yet that would "seriously disorient a bad guy"--and I've tried, from car headlights, alley lights, Costco HID, Boxer HID, Surefire M6, etc. By seriously disorient, I mean someone who didn't know which way he was facing, didn't try to escape in the most logical direction and could not move in a straight line. Anybody wanting to attack would only need to attack straight into the light.
A bright light has a secondary value of blinding the threat in the direction of the light so he doesn't know exactly what he's dealing with--multiple people or just one, police, security or citizen, armed with gun, handheld weapon, Rottweiler or unarmed, etc. That uncertainty might make some bad guys hesitate to attack.