As an American, I am automatically suspicious of any claim that video of a cop beating someone has been faked.
While we do tend to think that our cops are the best in the world at being unnecessarily violent against suspects, especially minorities and pet dogs, we are aware that cops in other countries are also capable of lesser brutality. Except in Scandinavia, where suspects are ordered into the comfy chair, offered the hot tea, told they have been very naughty, and given actual help towards not repeating their crimes--and that somehow actually works for them.~
We have a nationwide protest movement organized entirely around the suspiciously-high number of black men dying during police encounters or while in police custody. And every time, the video comes out, and the police say, "That isn't what it looks like. It was entirely justified use of force. We investigated ourselves thoroughly, and cleared ourselves of all wrongdoing. Thoroughly."
If an American cop can kill someone for "taking a fighting stance" and "moving a hand toward his waistband," I can consider that maybe Spanish cops might punch someone in the face for committing an overt and obvious act of rebellion against their national government, participating in an event that could sunder the political tranquility of the entire country. It might even be a really strong punch--like, enough to leave a bruise for a few days.~
Half of the U.S. is horrified at the idea of people getting physically attacked for the act of voting. The other half is sorely disappointed at the lack of blood in the streets. There may be some overlap.
Anyway, in the U.S., the police tell blatant and obvious lies whenever they get caught on camera doing something terrible. The cop-cheerleaders believe the lies without hesitation, and the cop-haters don't believe anything a cop says, regardless of the subject. So the only way to really counter video evidence is with more video evidence, from a different angle. All referees and umpires are blind when the call is against our team, but we will grudgingly accept video review of the play. All I have seen is the original video. I haven't seen the video showing how they faked those videos. In the absence of any such evidence, my default assumption is that the official government story is deliberately crafted prevarication.