If it ever came down to a shitfight between religious fanatics and the godless, given equal arms, I know where my money would be.
It's an interesting thought experiment.
One side, when thinking logically, shouldn't find value in a single life since we are all equally insignificant expressions of random chance. So they shouldn't have a problem with group thinking the few to suicide bomb for the many.
Except they will because humans are quite selfish in isolation and there is nothing to gain from it.
The other side have a party to get to after this war and dying gets them a better spot in it, they might value the life of the one more because it's a reflection of god's image in man, but they are keeping their eye on the prize.
They'll win because even if they die, they win and the atheists will take surrender and defeat over death and victory.
That's why religious fundamentalists are so scary. It's truly no holds barred.