Just another reason for the introduction of technology. The argument that it would slow the game is rubbish.
During the resultant furore around the decision whilst the players approached the ref and surrounded him and the linesman, the 4th official had plenty of time to look at the decision via the TV cameras, it would have taken all of 20 seconds.
It doesn't need to be used for every decision, just those inside the penalty area that are contentious.
If a decision is disputed in general play (studs-up tackle and possible sending off etc) each team could be allowed say two appeals per half, similar to those given to cricket captains in LBW decisions.
Over the length of a season such decisions as yesterday's can result in winning or losing a title or relegation, which costs clubs millions either way, which is why technology needs to be introduced.