it should not be banned because Muslims have to eat halal food, it is a part of our religion.
Kosher/Halal requirements should never supercede animal rights, and from the sounds of it, they currently don't.
If a stunned animal can still be considered Kosher/Halal, then there is no reason not to make stunning mandatory. In the rare cases an animal dies from being stunned, it should be handled in the same way as what must already be done for animals that die of other causes before slaughter (such as a heart attack).
Few points to point out:
1. According to Islamic law, any knife used to slaughter an animal has to be very sharp to give minimal pain to the animal.
2. The animal must not see the knife, or any other animal slaughtered.
3. The knife must cut straight through the wind pipe, jugular veins and carotid arteries in one sweep, but leaving the spinal cord unharmed.
The effect of this is something called brain death, that the brain irreversibly stops working, ending all types of sensations and feelings, including pain. Some may comment on the twitching ad turning the body does, saying that the animal feels pain, but its just the blood flowing out of the body through the cut, which causes the muscles to contract.
Thats as far as I know anyway, if I was mistaken in anything please tell me.
When stunned, the meat become polluted with hormones.
Quick slaughter in the correct way is best for the animals, they don't suffer.