Current hunter ethics have been evolving for a long time. Back in the 1800's, whole buffalo herds were slaughtered for the hides and not much else. The carcasses were left to rot on the plains. If you read through "Witchery of Archery" by Thompson, you will find many occasions where they took long shots at herons, etc., just for fun, and if they hit one, they would maybe take one of its feathers, if they wanted one, or just leave it on the ground if they didn't. When bowhunting began to become popular in the early to mid 1900's, people thought it was incredible that anyone would go hunting with a bow, mainly because by that time, there wasn't much game left out there to hunt! Some of our heroes from the 1900's, like Fred Bear, had hunting ethics (or lack thereof) that would raise more than a few eyebrows today.
I would imagine that if we had the chance today to get to know Maurice and Will Thompson, or Fred Bear, or some of the unknown buffalo hunters from the 1800's, we would like them and would want to get to know them better. I don't imagine their basic character is any different from our character today. Not enough time has passed between then and now to change the basic character of man.
Who knows what people will think of us 100 years from now? Will they hate us for burning through most of the remaining oil and polluting the planet? Or for some other thing we do that doesn't even occur to us as being questionable at the present time?
I think much of our ethics is based on hindsight. We look back at the way game was treated in the past, and it seems wrong to us on reflection, so we don't want to repeat or continue those practices. I'm sure the same is true with other ethical issues, such as slavery. We recognize Jefferson as a great human being and respect what he did on behalf of our country. But we believe he was wrong to hold slaves, even as we recognize that he felt no moral issues in doing so.