Can you report diamond players at the end of a game?

I just played a game where my team mates got smashed and didn't know until the game was over that we had a diamond player on the other side. Why can't we report that player? Once we find out he is a diamond player there should be a way to report that player. At least on the last status page of the game. He was so smug acting like he was such a great player but then I found out he was diamond once out of the game. He killed everybody with Nami a support character. He obviously knows something about the game we young players don't know yet. Why do you give an option to report unskilled players? Most players ARE unskilled when compared to diamond who you match us up with over and over again. Why does he have to be protected and remain hidden? Lets call him out and take his mask off. Don't allow that player to remain anonymous. The losing team should know they had a diamond player in front of them so they can report him if they want to. Who needs smurfs when we regularly get matched up to diamond players?