Some Pagans have even given up their day jobs to dedicate their time to preservation of a monument. The work is done voluntarily. Sadly, it's true that Pagans have been responsible for damage to sites, most often through ignorance. It seems preposterous that a candle flame can reduce stone to brown sugar, but once we have the information we do alter our practice. With Andy Norfolk, a Pagan based in Cornwall, I wrote the Sacred Sites Charter aimed at people who use ancient monuments ritually, and happily most Pagans have taken the information on board.
Information is a key to successful conservation.
If people have impartial information they can take responsibility for their actions. Most often they will alter damaging practices, such as lighting fires or standing on vulnerable bits of the past. Where there is little or no information people will create their own to fill the gap and it's often incorrect. Physical access to monuments is a more difficult issue. It is natural for authorities to want to guard something vulnerable but this can be counterproductive.