Why do you have to suffer through a game to report someone?

Here's a situation: Our top laner hovers graves, our jungler bans graves. Top laner proceeds to call everyone in chat "new at the game and retarded" amongst other things that I won't repeat to your sweet virgin ears. When we ask him to dodge if he's that upset he replies that "he's gonna have more fun feeding until he can afk" and proceeds to lock in disco nunu.{{summoner:2}} For some reason, the jungler thinks that "counter trolling him" will be the most effective way of handling the situation and locks in soraka.

So my question is: Why do I have to wait a minimum of 20 minutes (if they LET YOU surrender) before I can report someone? We have a chat log with enough verbal abuse that he would be banned regardless of the trolling and feeding. Why am I forced to dodge and receive punishment because i was rolled into someone that can bully their way into whatever they want?

I understand you can't ban someone for something they haven't done, but you SHOULD be able to report someone that abuses people in champ select. I just felt bad dodging knowing I was putting 4 more poor souls up to the chopping block..