First, let's not join this fight just because we are in the minority of the states that hasn't given total control of a river to the Federal govt. Before you jump on this boat think about what the designation would do. According to the Utah Rivers Council website, "Once designated... the river is protected from dams and diversions - forever." That means no more hydro-electric power will ever be generated by this river, ever. The designation also means no more water for agriculture along, or probably near, the 1/2 mile wide corridor it creates. Mineral extraction within the corridor would cease and/or never be allowed. It means that access to the river would be restricted. Roads would be closed and no new ones would be built. If you can't hike or afford to float the river the only way you would ever see it would be by pictures that somebody else took. Such a designation takes this water out of use for anything but recreation, and that will be limited to a select few that can afford it. We need water and minerals to survive. Why would you want to remove such a valuable asset.

Man Overboard--
In reply to your questions:
So it's still around twenty years from now. So that your children can see it and it will still be beautiful. So that future generations will have a little more respect for us.
If you can't afford to float or hike it (and you can do both rather cheaply if you're smart), I seriously doubt you are going to be able to afford the gas money it takes to get there anyway.

Actually, the Green flows into the Colorado and the water is shared with 6 other states so it's not like you just arbitrarily could take extra water from it without breaking the Colorado River Compact. So you're wrong about stating that it's only use would be recreation. The water is depended on for culinary use by a number of major cities and agricultural users downstream.

Man overboard;
You vastly overstate and distort the case. It's true, hydro development on the main Green would cease, but no one in their right mind is envisioning another big dam in one of these canyons.
The one half mile corridor is not a one-size fits all, it's just one way of protecting a Wild and Scenic River, if appropriate. I have floated Wild and Scenic rivers that had houses on the banks. New mineral extraction in the vicinity of the river would likely not go forward, but existing uses are routinely grandfathered in.
Likewise, road access is often not affected at all, in that existing roads stay put. New developments for access, would, on the other hand be controlled, but that's precisely what protecting the river involves. In any case, in the remote canyons that are the most prized feature of the Green, access is already severely limited by topography, not government. When I float Desolation Canyon, I don't see much road access because it's too steep and difficult and expensive to engineer a road in, anyway.

Yes, it's a beautiful river, and yes, everybody would like to see it stay that way. But Federal designations can come back to bite us in ways not anticipated today.

Is the river currently threatened? Then deal directly with the threats. Giving this broad designation seems drastic and over protective to me.

Worried about the Green? Start at its headwaters where a Wyoming rancher and member of the Wyoming Water Development Commission wants to build a mainstem dam. Despite years of studies and efforts otherwise, this idea is still alive and the state says it will hold a hearing in the fall. You think it is beautiful in Utah....