Would they? Even if this act makes them recycle less litter than they already do (recycling isn’t a fulltime activity), I don’t think it’s impossible they make people create less litter to such an extent that it dwarfs the amount of litter they could have recycled in the time this action cost them.

Considering “recycling”, at least of plastics, in the UK has been an alternative bin that feeds an incinerator or a landfill for years since China and the Philippines stopped accepting trash colonialism, I very much doubt they could.

I genuinely hope Stonehenge will survive the attack unharmed.

But you are not going to get attention for your cause without making a big fuss. Have you considered the possibility that they are just right in what they say?