I had never heard of these things before. Looked them up:
https://en.wikipedia.org/wiki/Georgia_Guidestones
A bit weird. The 'guideline' for a population of half a billion humans so that the world and nature is not destroyed is fantastical.
Most of the other guidelines seem very sensible eg 'Protect people and nations with fair laws and just courts'.
Anyway, I'm sure this bit of minor vandalism to an obscure structure in an obscure corner of the USA is significant.