We need to trust these guys. They are after all scientists and therefore very smart and careful. I mean really. It's not like these guys would ever make a mistake that could cause this thing to slow too much and enter our atmosphere.
And even if they did, how bad would it really be. Just a crater 24 miles wide and trees 200 miles away would spontaneously burst into flames but hey, there is definitely a small chance that it will kill a lot of people. And after all this thing could be worth something like 25 trillion dollars! Isn't it the little peoples duty to risk and lay down their lives so that extremely rich people can get even richer?