This isn't an isolated incident. I found that the summit cairn on Aodann Chleireig had been demolished, and the stones chucked randomly all over the grass. So I picked them up and rebuilt the cairn
I agree fully with the idea that daft tourist cairns should be demolished, but I find it bizarre that anyone would want to demolish a summit cairn or ancient well built cairns. Whatever next? Will people start blowing up trig points?