Environmental protesters say they are not sorry for creating an Extinction Rebellion logo on a chalk horse.
The logo, made of clothes, was laid on the Alton Barnes horse in Wiltshire, which had been recently re-chalked by school children.
Rob Sutherland, who led July's re-chalking, said the community has been "absolutely devastated".
He said children were "disappointed and upset" and "couldn't understand how adults could have done this".
James Noble, from Extinction Rebellion Vale of Pewsey, said the logo, which was added on Sunday morning, had been done to highlight "that we are destroying the planet we live on".
He said the work local people and children had done re-chalking it, "was a fantastic job".
"The last thing we wanted to do was to damage it. We were very careful of how we walked on it.
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"I'm sorry that it's upset people... but I make no apologies about upsetting people, we did our utmost not to damage the horse," he added.
The logo was removed by the owner of the land on Monday morning.
Mr Sutherland added: "I've had lots of people contact me in the past 24 hours. I've had to explain to children this morning - they can't understand how adults have done this.
"They've defaced something they'd spent their time and effort doing and they're absolutely disgusted.
"They're disappointed, they're upset, all of the anger's there.
"Most importantly it's just put them off the group [Extinction Rebellion] itself.
"You encourage children to do the right thing, you do positive actions and this just hasn't happened. It's completely the opposite."
The monument was restored over the summer with a RAF Chinook helicopter used to transport more than 40 tonnes of chalk up the hill.
The first attempt was hampered by high winds and driving rain, but the job was eventually finished in August when Year 6 pupils and their parents completed the facelift.