To be totally honest, despite the clear dissent and the fact it definitely should have been a yellow, I'm on the players side here. It actually looks to me like the referee changed his mind about showing a card, but then got confused in the second half because he'd written the name in his book before changing his mind.
You can see after talking to him, he gestures to send the number 11 away without showing a card. That's very unusual I think - I understand if the player walks away or the ref gets distracted, he might forget to show the card, but to consciously send the player away without doing so doesn't seem like something you could do?
Then after the player moves away from him, he turns and answers a question from the player in white behind him (possibly "why wasn't that a yellow ref?"). He then goes and says something else to the number 11 before restarting play - whatever he said at this point, you'd assume it it was clarifying if it was a caution or not. For the player to be so surprised when the red comes out in the second half, whatever he said, it can't have been clear and may have actually been wrong.
Having said that, I do notice he has neutral AR's. You'd hope they would have discussed at half time if a caution was issued or not - but again, maybe he looked in his book, saw the name and said yes even if he didn't mean to at the time. We don't know how busy the rest of the half was - if he's had a lot to do, it's very possible his intention had slipped his mind as well.