That's fair. Context is of course always relative. In would say context is given if the starts at the first interaction of the person taken in custody with the police. Of course its difficult to find such high quality footage. Not sure if it is worth to point out but many police officers are in favor of bodycams. They cannot use them because they are against the law in Germany. If I find a video with more context, I will get back to you, but I am pretty bad at that.

That being said: There are definitely police officers out there that love going on demonstrations and smacking people. I personally know one who did this who lost his job as a police officer; not sure whether it was because of that or something else though.