That land is valuable.
The federal government has the full authority to extract value from that land for the benefit of the public treasury.
Charging grazing fees has a long and established legal history.
Why should one citizen get to benefit from the land without paying? If Cliven Bundy has some mythical "right" to profitably use federal land, why can't any individual citizen just move there, build a house or a factory or an amusement park on it?
It's federal land, and the federal government has authority to determine its use.
... why can’t any individual citizen just move there, build a house ...
http://www.blm.gov/pgdata/content/wo/en/res/Education_in_BLM/homestead_act.html
It's American citizens land, and American citizens have authority to elect representative's to determine its use.
No, it’s public land. Anyone can use it according to cultural norms, with fees only to maintain and facilitate such land and use. It’s not there for profit, unless content is seriously removed or damaged (mining, drilling; in which case profit is a matter of compensation).