The fact remains that a person doesn't need any evidence to accuse another person of cheating. The presumption of innocence applies in the lobby. If you want to accuse Brabus of cheating, provide proof. If you suspect something, you can simply choose not to play with him. But to play with someone you suspect, accuse them of cheating during a specific game, and then not investigate... that's at least strange. That's why this action was considered a leave.