Regardless of whether you like it or not, athletes will always be role models for young children, and that's not necessarily a bad thing. Think about it, most supreme athletes have worked hard to get where they're at. Take Manchester City soccer player John Stones as an example. He didn't have a lot of talent, in fact, he had to play a year level below all of his friends, but he put in so much work that he now has the ability to play in one of the best soccer leagues in the world. Another example is rugby legend Richie McCaw. As a child, he was told he wasn't fit enough, so as soon as he got home from school he went for a run. He didn't stop at his fence. He didn't even stop at the end of the street. He went for miles, and then ran the whole way back as well. And although supreme athletes do questionable things at times, like Usain Bolt twisting his ankle while out clubbing, if our children can learn from their hard work and emulate that in their own lives, I know the benefits greatly outweigh the potential harms children can face from copying their idols. And besides, which 8 year old is going to go out clubbing anyway?
In sport (as in so many other sectors) the ones who got any kind of benefits and advantages succeed much more easily than others. Many athletes succeeded because of initial advantages: natural talents, the age at which they started practicing their sport,... They just have been lucky. Someone might say that their dedication should be rewarded, but there's a little thing to hold in consideration... They LIKE their sport. When you like something, it's obvious that you're much more motivated to do it. Do you know how many children or boys would like to practice a sport or an activity they like but they can't because their parents don't let them do that?
Admire famous athletes (but not only athletes) is a wrong thing, because they just did what they like without any restrictions and some of them had special talents that brought them to success. It's simple.
When it comes to morale guidance, social development, learning, the parents should be the ones teaching the kids, if your kid wants to hero worship a celebrity, that is fine, if it's not some celeb it's most likely going to be a cartoon. Just make sure you are the one that is the role model not the television.