Just throwing in my .02 cents here.
Athletes/Celebrities being bad role models I always thought was an overrated arguement when it comes to the effects on kids. A kids mother or father should be the example that they learn to live by, yes kids will always be exposed to negative things by the media including athletes, music artists, and movie stars, but I think the stuff thats more right in front of them should be the main concern, such as the parents, and also what kind of people they hang around and what their interests are. If a parent lets a kid model his life after someone who has no moral obligation to the kids it is a mistake.
I do however, agree with parents using an athlete as an example of the negative effects of drugs.
I got my drug talk from my dad by him shoving a big front page headline of Dexter Manley getting arrested for cocaine use in front of my face and him saying see what happens when you do drugs! Nothing good can come out of it. At the time Dexter Manley was both me and my dads favorite player on the redskins, along with Darrell Green, and from the experience, I didnt take away that it was ok to do drugs b/c Dexter Manley does it, instead I became scared of drugs b/c of how my dad reacted to it.
What was the end result? I still ended up trying pot in high school b/c my friends were doing it and I wanted to see what was so good about it, but I did it because I wanted to, not because it was the thing to do, and I stopped because I wanted to, without caring what my friends would think. Again, I think the primary concern of parents should be the example that the parents themselves are setting and also the crowd your son or daughter is choosing to hang out with. If you raise your kids to think for themselves, do what they think is right, and put them in the mindset that people should hang out with them for who they are and not because they do something cool, then youre doing a good job.