Arsenal should understand that when you target a player like Son early and often in a match, and get really physical like they did, the ref is going to pay special attention to what is happening with that matchup in an effort to keep the match under control, especially in a Derby. Son was coming off a brutal foul by Fabinho last week that deserved a red, and I'm sure the league was made aware of that. Son had already been kicked in the ribs while on the ground, with nothing being called either. All that adds up to a penalty being called when Son gets double teamed in the box, and a second yellow for Holding when he forearms Son in the face.
Arsenal can bitch all they want about the officiating. It doesn't change the fact they lost their composure in the biggest match they've played all year. They simply don't have the leadership yet on the field, or at the manager level. 13 red cards since Dec 2019, that's 5 more than any other team.
We really need Newcastle to show up Monday night.