We typically find from the past that those whose protests eventually succeed were initially ridiculed as idiots and law breakers... but eventually protests changed the mind of both the public and eventually those elected to make laws. We sometimes find that existing laws are written in a way to maintain the status quo and discourage effective protest - to cause change and modify public opinion may be seen by those who seek change as necessitating breaking law to some degree. For years, the cosmetics industry tested on animals and justified this by not risking consumers skin health... animal rights groups protested (and a good chunk of their protest broke law) but eventually public opinion began to move against the cosmetics industry
A.net readers may have strong convictions on this... but the environmental lobby have equally strong convictions as well - the public understands that they do it substantially for a cause and not for personal gain. The green crowd know that airports will shut down at any hint of a drone, and consider the importance of saving the planet to be of greater worth than civil obedience. If you want to treat people flying unauthorised drones at LHR on the same level as terrorists, you need to come up with very persuasive arguments
Whether the environmental crowd are right or wrong about Heathrow R3 will be judged long term by history and whoever comes up with the best arguments over environmental concerns that are discussed by the masses... sending protestors to jail for terrorism may backfire in public opinion if seen as heavy handed
Protest all you want.
But, in no way, shape or form are you allowed to endanger innocent bystanders lives; in this case, flying drones in the path of a commercial aircraft can endanger their lives.
You want to curb aviation? Go block the terminal so no pax can enter. Heck, even go invade the runways (the only life that'll be endangered is yours).
BUT, DON'T GO KILL OTHERS.