[Pyramid*]

a journalist told him to pose for the camera, after my friend questioned him why, he did it (yes foolishly), they (i think) slipped him a bit of money to swear and wear a "stolen" police helmet...

Your friend questioned the journalist why 3 times, presumably he got some sort of answer and then put his faith in whatever answer the journalist gave him.
If you know all of this, how are you unsure if he accepted money? If he did accept money, did put on a police helmet (which clearly wasn't his), did swear and did agree to have his picture taken knowing all of this was clearly a set up.... - I have no pity.

Journalist asks passerby to pose for photo. Passerby agrees, (you think) takes money, also agrees to be photographed swearing & wearing 'stolen' police helmet poses for photograph taken during petition - giving journalist the picture he wanted (with your friend's permission remember)... then complains because of what is written.

I'd say he didn't have a leg to stand on.