Good post Merrymaid, welcome to the forum and please stick around. Your post made it clear just what sort of damage was involved albeit more to the environment than the stones. Its quite hard to understand how mature people can be so short-sighted not realise the consequences of what they were doing and your analogy to the reaction they would receive if they did the same thing in a church or cathedral was well made .
I visited the Merry Maidens twice back in April walking there on both occasions before realising the was a bus stop nearby. A lovely part of the country indeed.