The incident had 2 noteworth elements.
The Fallaini elbows were absolutely disgusting and if there is any justice, some kind of retrospective punishment will be dished out.
However, he lashed out in frustration because, Dawson was it, basically had his arms wrapped around his waist and was restricting him from any movement. How that is not a penalty I will never know.
Referee and Linesman managed to miss them both