Well it depends what level she is. The assistants in the PL are generally not at a high enough level to referee in the PL.
Clear red for me. Commentator just said the penalty was punishment enough...no it wasn't because they missed it. Blatent wrestling to the ground...and I'm supporting Arsenal so not biased.
I wish more ref's would clamp down on holding and shirt pulling like Dean does. That said, surely most ref's would have given a penalty there.
That's irrelevant in determining the colour of the card. Dean's opinion was that Koscielny denied a clear goalscoring opportunity and therefore sent him off.
The commentator seems to blame the ref for 'ruining' the game...I would suggest it was the Arsenal player who has ruined the game. That was a tackle more suitable for the last minute of a cup game when you accept going off rather than concede a goal.
The reason it's not irrelevant is because if it was a foul it was automatically a red because it was obviously preventing a goalscoring chance.....................................