Actually, the Leave No Trace ethic says cairns should be removed whenever possible -- and it's the poeple who feel they 'own' the place that erect their own personal monuments in the shape of cairns. As somehow who has spent the better part of his adult life working with the USFS and non-profit trail associations, I can honestly say that 99% of all the cairns in U.S. wildlands are unnecessary and frequently misleading (marking the wrong routes, often dangerously so. etc.) At best, cairns are an intrusion that prevent the people coming after the cairn builders from experiencing the wildlands to their fullest. Kicking cairns is an act of reclaiming the wilderness from those who want to mark those land as their own.