Remember that the police were using this for extensive political capital against the Conservative Party, trying to draw a parallel between the shootings of police in Manchester and Mitchell's alleged disrespect in London, and the head of the police commission called for Mitchell to resign.
Obviously the police stitch people up all the time - it's easy to find people from any walk of life who would say 'well he was a bad egg anyway, he deserves it', about someone accused of something, irrespective of the truth of the matter.
The interesting things is to see this stitch-up played out so publicly, and towards a relatively powerful, well-resourced and respectable figure, rather than some scrote on a council estate.
This is an American tape, and we don't have the same rights they do, but the point is clear: . Never trust the police, try to avoid contact with them, they can fuck you over and it's not worth the risk.