No, dude. Listen:
Vampires have heightened senses. This means their eyes are more sensitive to light. Their ears are more sensitive to sound.
Now, if they are hit with a stun grenade, they'll be much more disoriented than a human. If a human is disoriented for say 5 seconds, the vampire is probably disoriented for at least twice that long.
Again, the link on stun grenades:
http://en.wikipedia.org/wiki/M84_stun_grenade
Upon detonation, it emits an intensely loud "bang" and blinding flash of more than one million candela and 170–180 dB within five feet of initiation, sufficient to cause immediate (but temporary) flash blindness, deafness, tinnitus, and inner ear disturbance.[1] Exposed personnel experience disorientation, confusion and loss of coordination and balance.
See? Blade will be blind, deaf, uncoordinated, and his sense of balance will be thrown off for at least a few seconds. How's he gonna return fire when he's like that? He can't. He won't. He'll fumble about like a deaf mute.
Hit Girl calmly walks over and unloads in his head.
I don't know why you are even attempting to argue this. There is no arguing this, it's fact.