Iraola was adamant they deserved victory after seeing Newcastle midfielder Joelinton escape a red card and Dango Outtara denied a later winner by VAR.
"It is very difficult to digest," he said after the match.
"It is obvious what happened. I think we should have won the game. I will complain now. Nothing will happen, I am not against the referee. He gave the goal, he didn't have the chance to go to the monitor and watch it. If he did I am sure he would give the goal. They will say it is a factual decision but it is not a factual decision.
"The ball never touched his skin, we have very short sleeves, so it touched his shoulder. The referee could not do anything else, someone call him and say he had to disallow it.
"No one will remember this in two weeks. I am very frustrated.
"They are telling us they will give more power to the referee. Now, I cannot do much more."
On Joelinton not being sent off for a foul on goalkeeper Neto, Iraola also said: "I don't even want to speak about this. I complain now about other things, I think why we didn't win is very clear. We didn't win today because of this. I don't care if they show a red card or not, it won't change the game, what will change the game was the goal they disallowed from us."
