Their disappointing draw at the Liberty Stadium hinged on an 81st-minute incident, when Dean awarded the spot-kick and sent off Swansea defender Chico Flores, even though his foul on replacement striker Glenn Murray appeared to happen outside the penalty area.
Dean may well have still sent off the Spaniard, penalty or not, but given that he pointed to the spot while running more than 35 yards behind play, Monk was surprised he gave it
Murray converted to give Palace a share of the points in a 1-1 draw.
"One hundred per cent, outside the area," Monk said
"For me, why is the referee making a decision from 60 yards away that he clearly has no view of being able to tell that?
"I looked straight at him and he didn't confer with his assistant, or his linesman, and the linesman's not flagging for anything
He's not flagging for a penalty, so he (Dean) has decided to make a bizarre decision.
"The lead-up to that incident, we should have dealt with better
We caused our own mistake.
"It was like he (Dean) couldn't wait to give the penalty and he couldn't wait to give the red card
The red card I'm not so sure - maybe it was, maybe it wasn't - but the penalty is not a penalty."
Jonathan de Guzman gave Swansea a first-half lead, as they bossed possession
The late penalty came from a mix-up between goalkeeper Michel Vorm and his defence.
They failed to clear a ball over the top, allowing replacement striker Murray to toe-poke it past the goalkeeper, 20 yards out.
With an open goal beckoning Murray was brought down and Flores saw red
Murray cracked the penalty into the top-right corner.
Palace manager Tony Pulis saw the incident differently to Monk.
"I think the first touch is outside, but if you have a look again - only from a Crystal Palace point of view - he does touch him again inside the box," Pulis said.
"In the second half we played a little bit more on the front foot, we turned their midfield players around and made them defend a bit more and I think the longer the game went on in the second half, the more dominant we became."
Pulis announced he will fine substitute Jerome Thomas - who apologised to the referee after the game for diving - and Marouane Chamakh, who also dived in the first half.
"I just don't have it at football clubs I manage," Pulis said.
Swansea's bad luck was not confined to the penalty decision.
Their captain Ashley Williams was up all night with sickness and was even sick on the pitch, before being replaced in the second half
Striker Wilfried Bony had also been sick before the game and was taken off in the second half.
In-form midfielder Pablo Hernandez had to be withdrawn in the first half, suffering a hamstring injury.
Monk added: "In terms of what we've been through, I couldn't have asked for any more from them."
He was proud at how his side dug deep during the latter stages and held on to a point, adding: "If you can't win a game the next best thing is not to lose it and if we had lost that game it would have been an injustice, but we didn't which is great from my perspective."
Having seen his charges dominate the first half, but fade badly in the second, Monk said everyone is now glad of a break before taking on West Brom on March 15.
Pulis felt his side deserved to take something from the game after their second-half performance and was delighted for goalscorer Murray, who he said has been working seven or eight hours a day to get fit after a long-term injury.
"It's a great result," Pulis said
"We're delighted to pick up a point at Swansea."
Source : PA
Source: PA