He's already done enough, so stop yelling at him unless he actually does something to deserve it. I don't remember the exact details since I was barely conscious at the time, but you're not the only one here with a dead family and Otonashi was the closest that he had to one. Just give him a break.

Oh, and the whole God-is-better-than-all-of-you thing is just his personality all the time, by the way, that's not just because of right now. He's just a brat.