Personally, I don't think MD should have gotten in trouble for going to an agents party (albeit funny though). The difference here though RWS is that the violation directly involved Marcel himself. Again if Cam had known about the money, or had asked for it himself but still went to Auburn he would be suspended right now.
Still, he didn't know. All he knew is that his friend invited him to a party that other football players were goingto be at. I do agree with your reasoning that the MD involved the player himself. Obviously had he not gone, nothing would have happened. My point is the NCAA used their discretion to say "Ok, Cam didn't know anything about what was going on behind the scenes. We'll let it slide." Why can't they use their discretion in a case like MD to say "Well, he didn't know it was being thrown by an agent, and he doesn't even know who the agent is."? That's the sort of can of worms that has been opened.