As FTS said, of course professional athletes, and maybe to some, even college athletes can be heroes. Anyone can be a hero to children if you think about it. Even through legal trouble or discretionary issues that should be kept private, such as the Tiger Woods thing. My friends are golfers and are huge fans of Tiger, even through his debacle, they are still some of his biggest fans.
Personally growing up, I loved Frank Thomas. He was amazing with the bat, and was passable at first, just don't let him throw. I wouldn't hear about any bad things coming from Frank. The MLB didn't market him as the face of the sport, so he probably wouldn't be a hero or looked up to by many people other than Sox fans.
Or I'm sure some young kids that love College Football have Tim Tebow, or some old Vince Young or Reggie Bush posters on their walls when they were in college. Athletes are looked at as role models for how kids should act. Because of the publicity, some of their indiscretions, even if they are minor, get blasted in the public. But for the most part, athletes can be heroes, hell I still have a few that I look at as heroes, and I'm 19.