Ah yes, it's holding back the massive sweeping wave of change currently going on to fix climate change.
No, don't be a dumbass. It's raising awareness, because it's obvious nobody is giving a shit about this really fucking massive problem that is directly on our doorstep. Painting Stonehenge isn't going to accomplish anything except be a nuisance, but being a nuisance is how you compel people to get shit done non-violently. MLK and his sit-ins pushed civil rights forward by being a nuisance. Gandhi pushed Britain out of India by being a nuisance. If you accept the status quo, the status quo will remain. You have to get out and make noise and attract a following if you want the folks in charge to pay attention to your existence.
Trust me, you want them painting on Stonehenge for attention. This is the non-violent option. When this is ignored long enough, the non-violent option will be shelved and that's when people will suddenly start paying attention.
"Those who make peaceful revolution impossible will make violent revolution inevitable." - John F. Kennedy, 1962
MLK advanced civil rights by being a nuisance. Gandhi pushed Britain out of India by being a nuisance. I'm sure there are others.
It is in the nature of protest to be disruptive. It has to be. If it isn't, it gets ignored. Climate change is getting ignored. What would you rather they do, go deface an oil refinery? That'll just get them arrested and the news suppressed. Big public displays that can't be hushed are the only way to make sure your message reaches the world. These folks have been considerate enough to make sure that message didn't permanently damage its canvas. I don't know what more you could ask from them.