I will bet you a large sum of money that the only difference between you and a christian 10 year old boy is that they don't spend all loving day on the computer and have morals. Your 10 and cursing. Maybe you should try slowing down.
Or maybe you could take in the fact that he's already been insulted repeatedly and people aren't perceiving his own religion after his grandfather's death.
I can relate. I only came back from my grandmother's funeral yesterday. Sadly, I didn't know her well, but she was an incredible woman. I'm not sure what I believe in as an "afterlife", but I do take comfort in the fact that she's no longer in any pain or danger.
I suggest that you do the same. I won't try and feed you a bunch of bullstuff about my certainty of religion, but at least understand that he won't be in pain because of his old age or in mortal danger anymore, and that he hopefully passed peacefully and left good memories in his wake.