Respect All Laws, Regulations, Guidelines and Policies of the U.S. Forest Service
The forest service policy on geocaches on their lands is generally understood to be that if geocachers abide by all laws, policies, rules, and guidelines within a national forest, then it’s alright to geocache there. Since the U.S. Forest Service is made up of hundreds of different forests with different names, managers, employees, concerns, and policies; some of the rules and what they allow are also different. It can be looked at like the many different sovereign states that have some latitude, but still fall under the authority of the federal government. But on a whole, so long as geocaching enthusiasts abide by all existing regulations, including motor vehicle restrictions, not damaging any trees/flora/fauna, causing no impact to streams and wetlands, it will generally be considered acceptable. Peter Hubball wrote a great piece on Biodiversity: Why Conserving Wildlife is Important for us.
Furthermore, geocaches should be hidden appropriate areas. Inappropriate placements would be somewhere that impacts historic buildings, monuments, interpretive displays, landscaping, weather stations, archeological sites, wildlife, and riparian stream sides. If you want to mouth off or get huffy with Forest Service employees, you’ll only ruin it for other friendly geocachers. Don’t fall prey to an overly heightened sense of self-importance.