I would say I agree!! If the boy wants to play then let him. I don't think parents should force kids to play sports. But should encourage them to play. I come from an area that did not have Youth football like we do here in TN. All we had were Pop Warner Leagues and Boy's Clubs. These groups were good but they had a hard weight limit. kids couldn't weight over say 120 pounds. And there were no Middle School Football. That ment that the bigger kids in 2-8 grades didn't play football until the reached High School. That hurt a lot of kids. They didn't have the fundamentals of other kids. I have seen were kids wait until they reach 7th or 8th grade to start playing. They struggle big time trying to catch up. And don't start unless they are a great athlete.
It is true that you as a Parent can burn a kid out. But that can happen in any sport. Be it Baseball, Basketball, Soccer, Chearleading, whatever. The Parent can't push it down a kids throat. I was one that would let my kids play whatever they wanted. But if you start a sport then your going to finish the season. If you don't like it or you don't want to play next season then that was fine. They tried it and if they don't like it then fine. Now we Know!!!
As far as football if the parents are on the smaller size then more than likely the kid will be small. And if the kid likes football. Then start him out early and get the fundamentals. Don't wait till he is in Middle or High School to go out and not have a possitive experence. Then he might quit on something that he has loved from afar because he wasn't taught how to play. Playing on the playground isn't the same as when you put pads on. So let him learn young and enjoy the experience when he get's older.