How do i report this "people"?

you don't. Stop crying over what someone said and hit the play another game button.

Riot has access to the pre-game and post-game chat logs.

Just report them normally and it will be detected.

If you didn't report them after game you can submit a ticket to RITO, but I'm not sure it will count as a report.

If someone is showing toxic behavior in pre or post game chat, you can still report them through the in-game report system. Just be sure to leave a comment specifying that you're reporting for pre/post game chat when doing so.

You can report them and specify toxic post game chat but nothing will happen.

Eventually it will be added to the Tribunal AI.