Violent offences against third parties

Bas Nijhuis was in charge of the Eredivisie match between Ajax Amsterdam and AZ Alkmaar yesterday. In the 36th minute, a "fan" stormed the pitch and was violently detained by the Alkmaar goalkeeper, the consequence of this mindless action must be the red card, Nijhuis issued it correctly and it appears important to me to point that again out. What happened then may be seen as scandale. 

After a quick conversation between players and their coach, AZ Alkmaar decided to boycott unified the further game. An understandbale reaction, but according to the rule, Bas was right, even though one has to emphasize that AZ's decision to boykott the game was potentially not due to the decision but more likely due to the overall circumstances which are shown by these screenshots and pictures:

Verbeek explains AZ Alkmaar's boycott

Nijhuis in the post-match press conference

Nijhuis explained his decision with rule 12 which says the following:

"A player who commits a cautionable or sending-off offence, either on or off
the field of play, whether directed towards an opponent, a team-mate, the
referee, an assistant referee or any other person, is disciplined according to the nature of the offence committed."

This means that it does not matter whether it is a player's opponent or a third party, it therefore has to be red. Nijhuis also stated in the press conference that the goalkeeper's reaction had trespassed self-defence as he had kicked the supporter two times after latter had already lain on the ground.

What remains is the fact that it was a right decision by Nijhuis and an understandable reaction shown by AZ.

UPDATE:
The Dutch federation has undone the issued red card as the federation thinks that a red card was in this specific situation not imperiously necessary.

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Something similar happened in Greece a few years ago.