If it's all found to be true, then yes USC should be sanctioned. I have no problem with that, and I won't make any excuses for that.
They have to show some evidence that USC had some knowledge of it, and so far I don't think there is any such evidence. NCAA used to come hard on schools in these "agent" cases, which doesn't make sense since the agents aren't trying to help the schools, in fact they are working against them. But in recent times NCAA has been more reasonable. Michigan didn't receive any penalties in the Woodson case because NCAA said they had no knowledge. But then again NCAA is always unpredictable, so anything could happen.