And this, as a counter-argument to my statement, is a fallacy itself.
The problem you mentioned isn't caused by the object itself - the marijuana - but rather by the behavior which merely utilizes that object. Remove marijuana and replace it with any other number of things, e.g., other drugs such as alcohol, sex, etc., and the problem still exists and is the same. In your scenario, marijuana didn't cause the problem and, in fact, isn't the problem; it's merely a symptom of the problem.
Which was exactly my point: while marijuana is often used by people with problems, marijuana - in and of itself - rarely if ever causes problems.
I love it when people try to use logic but suck at it. It's great for a laugh. A fallacy is a bad inference -- yours involved some version of the genetic fallacy -- "The genetic fallacy (also known as the fallacy of origins or fallacy of virtue) is a fallacy of irrelevance where a conclusion is suggested based solely on someone's or something's history, origin, or source rather than its current meaning or context." Please which fallacy did I use?
Your claim, that there are no dangers of MJ to talk about hardly needs to be "disproven", but if you like, it can be disproven by your own admission, namely, that it can be abused. That which can be abused surely has some dangers worthy of being talked about.
You are correct only this far, that neither alcohol nor MJ cause a person to consume them. After that, what you are saying is hard to take seriously. This reminds me of the guns don't kill people, people kill people argument except applied badly. It is definitely true that people choose to pull the trigger, and in that sense it is people who kill people. But not even the most ardent gun's rights activist would be so silly as to say the bullet wasn't the cause of death. Of course alcohol causes its effects, and so does MJ. That's why we use them... they work.
Saying MJ doesn't cause any problems is foolish. Of course I think many forms of substance abuse have deeper or prior causes like emotional problems. Then again, sometimes irresponsible young people just make bad choices. And sometimes responsible people choose a course of action which is good in itself but has negative side effects. All of these situations have dangers worthy of being talked about. It's not a one size fits all position. One thing is clear, however, that the use of MJ has plenty of possible pros and cons, all of which are a direct result of the properties of the substance itself, and not merely a property of the choice to use it. It is sheer wishful thinking on your part to imagine a substance that strong with only positive effects. It is not I but the vast experience of humanity that refutes you.
Anyway, this argument about the argument is off topic. I'm satisfied with how Coach and the school handled the situation, I really hope it works out for Tim, that he is effectively free to make good choices, and I think either extreme is pretty much just that... extreme.