I found your post to George Knapp wanting some evidence of Slazar not wanting horses on the range and decided to go looking and found this - Cameron Bryce, a BLM ecologist wrote that "wild horses do not belong in western ecosystems" - in the attached link.
"What is truly motivating BLM’s massive roundup strategy? It would seem to be a deadly combination of their belief that wild horses do not belong on the range and that the land should be used for extractive purposes: livestock grazing, oil and gas development, uranium mining, siphoning off of water etc. Cameron Bryce, a BLM ecologist, wrote that “wild horses do not belong in western ecosystems,”
Continuing onward I saw on http://rtfitch.wordpress.com/2010/07/16/blm-%E2%80%9Cwe-are-not-the-bureau-of-horses%E2%80%9D/
a reference to an Environmental Assessment where I think the quote initialy arose -
Overview of Current Situation and TCF
The Cloud Foundation - dedicated to the preservation of wild horses on our public lands, and the protection of Cloud's herd in the Arrowhead Mountains of Montana.