I'm not sure I understand your reasoning on this one. Do you think this law should not exist because everyone already has a date and time they will die therefore it is futile to try to prevent it? If that is your opinion then I will respectfully disagree. If I misunderstood your post then please forgive me.
If I choose to go skydiving and my parachute fails to open, then yes that was my decision and I assumed the risk. If my child(ren) are standing at their bust stop in the morning waiting for the school bus and an irresponsible driver wanders off the road and mows down a group of children that were doing nothing more than waiting for a school bus all because they felt it was important to text, check facebook, or anything else on their phone, then no, it is not ok, it was not time for those children to die, and the driver should be held accountable.
Google: "texting while driving accidents" and watch some of the videos. They are most certainly avoidable. Here's one about a driver that was convicted of vehicular manslaughter: