This would seem to be an even bigger reason to join. Join the league and make it effective and powerful! If the aggressive powers would have had to face the anger of the gathered world community, instead of just this or that wavering and pacifist single great power, WW2 might have been avoided.I think by the time FDR came in a lot of people thought the LoN was ineffective. This was after the Japanese invasion of Manchuria and Germany and Japan's withdrawal from the league.