I take issue with this. They think someone is guilty of a real, serious crime, but they can't prove it so they want to convict them of something else. That is bypassing the concept of "innocent until proven guilty".

Police can already arrest the people making the videos (if they were in the UK or US) without having to make it a crime to simply view the video.

I don't buy the argument that these videos are propaganda to recruit -- they are there to stir fear and incite the idea that no one will save you if you are captured. The goal of the videos are to bend the public opinion.

The video will only sicken the majority of US and UK citizens -- which will in turn demand direct military action. This is, what both administrations (US and UK) have been trying to avoid recently as both have campaigned in large to avoid any direct use of the military (aka, boots-on-the-ground). It would be bad, politically, to then renege on that and send troops in.