It dropped the ball on the 'possible reality' but i think the main theme is about games.
Whoever play or played multiplayer games knows How this goes:
People that are kind and normal persons sometimes become shitty people when behind the screen. And i include myself in that. I try my best to be a friend gamer, but sometimes i cant avoid being toxic on a game for a reason or another, and scream and curse people.
And some players go 100% toxic all the time. It is a safe enviroment to be an asshole, because people cant punch you in the face.
I think that is the main point of this episode.
And that May be the espisode problem. I guess a big part of the Black Mirror Audience havent played online multiplayer games.
I think it's applicable to a lot of types of games. Sure online games are relevant, especially since you're dealing with real people but because of the filter of the game they don't seem truly REAL (much in the same way Daly probably rationalized that his victims weren't real). I was also reminded of games like GTA, The Sims and Roller Coaster Tycoon, where just about every player at some point has just decided to slaughter helpless simulated people for amusement. I know I have. There's something oddly liberating about being able to do things with no consequence. For me the fact that the lack of consequences included that no real people were actually harmed was a bonus, but for some out there this is a drawback, which is a scary thought. So yeah there are good concepts in this episode but the execution just ruined them for me.