The same way the believing soldier/sailor/airman/marine does: He does his part, whether it be servicing tanks, patching up troops or pointing and firing weapons at the enemy. The enemy dies just as quickly from an atheist thrown grenade as any other.
You missed the point. Our rights are given to us by God; therefore, nobody can take those rights away. If one does not believe in God, where do these rights come from and who can then take them away?