Do you actually not realize that saying something insulting or dumb, getting called on it, and then stating that is more on the reader than the poster - is insulting? It's the same as considering "I'm sorry that you feel that way" a valid apology. It's just as dumb.
Linesmen in the NFL are making 7 figures for understanding exactly what they need to do, and the hundreds of ways to do it, on every play. Linesmen on a high school football team are a different discussion, and will range from those that have been doing it for years and those that picked it up last week. It's not a demeaning statement to say that people come in to playing football later in life, as playing it as it is actually played as you get older here in the US requires bigger, more mature bodies than all pre-teens and many teens are going to have.
The insult to football players in general compared to soccer players stands on its own.
The hours thing by Gladwell and company is overplayed, and is already on the downswing. I've met him a few times, I've read him, and I'm telling you, you probably shouldn't be taking his ideas and quoting his thoughts very far - they won't age well. Even in the team you are probably most familiar with, whichever you would consider your son's primary soccer team - rank the players on that team from top to bottom, by whatever measure of goodness (except hours spent) that makes the most sense to you, whether impact to the team, goals scored, ball-handling, etc. Then rank them by number of hours spent per week that they spend bettering themselves, in group practice, individual training, and game time. Plot both of them. If hours spent trying to to get better (and continue to improve) was a reasonable metric to measure skill, you'd have a very close correlation between the two lines. But since it doesn't really work like that, there will probably be very little correlation. Some of the players are going to be awesome, and spend comparatively little time outside of practice, even if they make them all. Some of the players are going to eat/sleep/breath soccer 24/7 all week, and they still will rarely touch the pitch on game day. Many would call the first group the skilled ones and the second less skilled, unless skill is redefined to mean nothing but how many hours are applied on task.