Designating an area a national monument ties the hands of subsequent governments to do with it as they please.
On the other hand, every other way of losing public land also ties the hands of subsequent governments to do with it as they please. Suppose that you sell it for a song to your friends, or allow resource extraction in an environmentally sensitive area... A decade down the road, you can't wave a magic wand, and undo that damage.
The fact of the matter is that once public lands are lost, they are gone - forever. Every election year, we must fight to keep public lands public - we only need to lose once, and then its over. Can you really blame someone for seeking a more permanent solution to this problem?
On the other hand, every other way of losing public land also ties the hands of subsequent governments to do with it as they please. Suppose that you sell it for a song to your friends, or allow resource extraction in an environmentally sensitive area... A decade down the road, you can't wave a magic wand, and undo that damage.
The fact of the matter is that once public lands are lost, they are gone - forever. Every election year, we must fight to keep public lands public - we only need to lose once, and then its over. Can you really blame someone for seeking a more permanent solution to this problem?