[Hoot Gibson]

This seems so obvious: the fact that Ali declined, EVEN THOUGH HE WOULD HAVE HAD LIGHT DUTY, proves the point.

Ali would have missed some huge paydays had he served in the military. As it turned out, Ali missed out on some big purses anyway when every state boxing association refused to grant him a boxing license because of his stand on the draft. So, the fact that Ali might have been assigned "light duty" had he served in the military, is not proof that his motives were pure because there was a large financial incentive to avoid the draft.

You can argue that Ali would have been better off pulling "light duty" than dodging the draft, but Ali had no way of knowing that in advance.