Not safe? Maybe. However, it wasn’t his decision to make.
Exactly, if it bothers someone, don’t go to the Park, report it. These Scouts, Scoutmasters themselves could have been hurt knocking rocks over.
Maybe one has to live in the Southwest to appreciate this because I’ve seen similar places, “City of Rocks” near Deming New Mexico and the like though Utah is famous for these places and even has a National Park or Monument.
http://beautifulplacestovisit.com/wp-content/uploads/2011/05/Arches_National_Park_Utah_03.jpg (big picture, just leaving the link)
Not my place to disturb a place before others see it.