The penalties prescribed in the ANO for endangering the safety of an aircraft are quite eyewatering, I suspect if anybody does manage to fly a drone across Heathrow airport in protest they will be looking at a significant prison sentence.
I doubt the airport authorities will be caught on the hop a second time.
Most people agree that human activities are having an effect on our environment. There are, after all, 7 billion of us on the planet. (I believe it was around 3 billion when I was born). To suggest that that sort of increase would not have an effect would be bizzare.
The disagreement, seems to me, to stem from ideas about what we should do about it. People like these extremists want to push a narrative that nothing less than the extinction of the human race is on the cards. (As evidenced by one the the Extinction Rebellion organisers I heard on LBC radio saying we had 18 months to act or we where basically all going to die). This is nonsense.
I'm not even sure these protestors believe it - I suspect that the environmental movement to them is basically a vehicle from which to push their (extreme) political views by inserting an urgency into the debate of such a degree that 'tearing down capitalism' is the only solution. When they use the phrase 'we need a new type of politics', as coined by that young Swedish girl, they basically mean marxism.
I, like most people, are all for sensible actions to preserve the environment. Nuclear power would be a good start....