I don't know. I figure the point is at the very least arguable. This is football we are talking about here. Big Baby chose the right sport, unfortunately for him.
In this sense I think toughness is a similar attribute to leadership. You can probably teach a player to be a leader but you would rather have someone that is a natural born leader.
In no way can you teach toughness. I have seen many players who were tall enough fast enough and athletic enough just to be tossed to the side because they alligator arm balls thrown over the middle. You cant teach reflexes.
For what it is worth, my UCLA buddy said he was a great coach. Judging his resume, he looks pretty good. Nate Burleson and Brandon Marshall alone make that list pretty impressive.