It seems like he did the right thing by telling the person not to say it and then move them to another channel to speak to them about it I would consider this a job well done. On another note if he was breaking rules by saying offensive things you are allowed to record ( 4 - No recording. You can only record when another user is clearly breaking rules. ).

It's really annoying how you handle this without knowing the whole story. If you don't know about anything you should spend time finding me and asking me anything rather than assuming.
I wouldn't make the report abuse if he told the person not to say it but he didn't. Also, I can't record things that happen in the past so I don't see how I could get proof of that and I can't see into the future to know when they are going to break rules to record.