Redskins is NOT a bigger slur than the n-word. Not saying it isn't a slur, but as bad or worse than the n-word? Sorry, but no.
As for players saying a word they grew up saying, sorry, but that is no excuse. I grew up in a neighborhood where the majority of the kids called bottle rockets "n-word chasers," but once I got old enough (early teens), combined with my parents always telling me that that word was wrong to say, I knew better. In other words, a learned behavior can always be unlearned. Besides, no one should be using that word, so while I think trying to police it on the field with penalties will be difficult, I think the possible rule comes from a good place.