The decision has been taken by the referee and it will be useless caused by blaming the referee will not change the situation. Arsenal must have accepted its first lose this season. You must also see the previous case related to the VAR. It's always become a disaster.
The technology has made decision making in football very inconsistent. The same decision that has been taken in favor of one team will not be the same in another game involving another team. The officials behind the technology should by now have recorded these cases and the judgements that ruled so that they will be able to have a reference the next time similar situations happen. Arsenal's record of not loosing any game has been spoilt because of bad decision from the referee.