Most European carriers (including KLM, Lufthansa, Air France, Transavia, and Ryanair) explicitly state in their conditions of carriage or safety announcements that capturing other passengers or crew members on video without consent is forbidden. One instance they actually used the PA system to say to not record other passengers. As far as I've seen, it's not heavily enforced as long as you're doing holiday pics but the moment somebody starts harassing someone else with recording they turn on the harasser.

It's a bit of a grey area. Filming in public places is generally allowed, but an airplane isn't really a public space in the same sense, since you need a ticket to enter. I guess it would also depend on the airline's terms and conditions.

fair point. they didn't ask to have their face plastered on social media, even by those who agree with their actions

The law in many countries is actually pretty complicated.

It's usually legal to film in public and to get people in your scene as long as they are incidental to the filming - they can't expect total privacy as it's public.

But if someone is aggressively recording, or doing so when it's clear the person does not want to be recorded, that may be considered as harassment or otherwise illegal.