Monk felt aggrieved to have had two first-half penalty appeals turned down by referee Graham Scott.
There did not appear to be any contact when Leeds left-back Charlie Taylor went down in the area in the 40th minute, but the home side felt they had a cast-iron case three minutes later when Ronaldo Vieria’s shot hit Jack Colback’s raised arm.
Benitez said: “You can talk about that for half an hour but it wouldn’t change too much because in the end we (played) a good game against a good team.”
But Leeds boss Garry Monk felt it was a clear penalty and said his side had been unlucky with several key decisions.
“The game was decided on critical moments, to be honest with you,” said Monk.
“Against a side who are top we competed very well. Our attitude and commitment to what we were doing was very good.
“I just felt we got on the wrong side of those critical moments and had we not, we would probably have got a result.”
The former Swansea boss added: “In my opinion it’s a clear-cut penalty. I’ve had many penalties given against myself or my team for much less than that. It was a clear-cut penalty.
“But those critical moments, we fell the wrong side of today.”
Former Crystal Palace forward Gayle, 26, a £10m summer signing, took his goals tally for the season to 13 two days after it was reported he had been punched unconscious during a night out in Liverpool last week while celebrating team-mate Jamal Lascelles’ birthday.
Magpies manager Rafa Benitez said: “It’s quite difficult for me to decide whether I play Mitrovic or him because they’re both training really well and both scoring goal.
“I have a lot of confidence in both, it’s not a problem because you have to analyse how they are in the training sessions.
“Dwight was training with us and not with the national team like Mitrovic, so it’s always an advantage.
“But Mitrovic is training really well and it was a great goal (for Serbia) against Wales.”