I am not a fan of the Rainbow events working their way around the system and letting other users of the National Forest and the taxpayer paying the bill but think of all the public events that occur on the national mall that follow the rules yet the taxpayer foots the bill.
The fact that they still are out there attempting to mitigate the impact is a positive thing. Trees and the understory will grow back, as long the stuff that will not rot gets hauled out, the impact to the woods is probably about the same as a logging operation. Its looks like crap for a few years and then the woods come back and covers it over. ATVs also have impact and I expect if the linear impact of the 1000 plus miles of ATV use is probably more than the concentrated use of the Rainbow site.
BTW while accessing the AT corridor in Maine last week, we occasionally used and ran into bootleg ATV routes off of logging roads. The scars they leave will take a long time to heal. Unlike a logging road there is no gravel base so the mud just keeps getting deeper. The route went near but not into the AT Corridor which was one of the reasons we were out there to more clearly delineate the boundary.