I think we agree on a lot. What I am pointing on in this situation is that it is not the party goer's responsibility to police the party for alcohol. It is very true that sometimes the cops just charge everyone in the general area and the judge just rubberstamps the charges. This doesn't make it right, however, and really shouldn't be applauded. It's lazy police work and reckless behavior judges.
Police do this all the time and its reprehensible. It occurs with motorcycles where one group might be driving recklessly, and the cops ticket every rider they see - even if it is the completely wrong group. It basically reverses the system and presumes the charged to be guilty and must prove their innocence.
Going back to the case in the article, depending on the laws in the state, if the police can't pinpoint the possession then no one should be charged.
As is usually the case in an incident like this, there are many conflicting accounts and the full facts and circumstances are hazy at best. Nevertheless, I think there is one point on which there can be very little doubt and upon which I think we can probably all agree and that is that none of the cops's kids were invited to this party...;-)