I would argue it before hand but now I have to agree. The sport of American Football was more violent then rugby at the time. If they didn't add padding or helmets, the sport would be banned.
Other sports would take it place like rugby (for me rugby league would work as a American Football alternative then Union) , lacrosse, basketball and hockey. Baseball will still be king but there will be a huge gap to fill with American Football out of the way.
Nahh, I simply don't agree with post-Roosevelt reforms gridiron of the 1920s being more dangerous than the rugby codes - remember that the breach between Rugby League and Rugby Union happened because of players wanting to be compensated for Broken Time ... which was the need for players to take time off from work because they got injured playing rugby.
The Roosvelt reforms to gridiron made it a safer game by creating more open plays because of forward passing and fewer mauls because of banning linking arms and so on.
Without the ability to use the head as a weapon that helmets give, helmet-free Gridiron is an even less dangerous version of the same game.
You dont need to lead with the head on either defense or offense - it is simply bad technique that restricts being able to see opportunities. Heck, look at the absolutely explicit adoption of rugby tackling by the current Seattle Seahawks team (*), which arguably has had several of the bets ever NFL defenses. And as far as putting your head down with he ball, look at any of the great running backs and you'll see they don't do it.
As Jack Gibson said when describing the differences between League and Gridiron ... 'Same game, different rules'.
(*)
- note the film in this taken from Union and League.