I'm not a big fan of using, or more correctly over using flashlights. If it will take out your opponents night vision it may well do the same to you. Handy pieces of equipment, but I think their use is over emphasized today.
Back before lights became as bright as they are today, one technique I was taught was aim low and left (most folks used to use the high and to their left hold to keep the light from being in front of their body in case your adversary fired at the light.
With weapons mounted lights (I won't use them) being common today, I'd likely fire directly at the right. Pretty good odds of hitting at least a hand or arm, and darned good odds of hitting the torso or head. Heck, even techniques such as the Harris method, shooting at the light was a pretty good idea.