The England defender blew his top at something Maupay said to him in the closing stages and had to be calmed down by his manager.
City skipper Walker had been subjected to taunts about his personal life from the home fans throughout the match.
Guardiola had a long conversation with French striker Maupay after the final whistle but when quizzed about the incident afterwards, Guardiola simply snapped: “Next question!”
Guardiola was happier talking about hat-trick hero Phil Foden after the victory in west London which, coupled with Arsenal’s win over Liverpool on Sunday, left City two points behind the Reds with a game in hand.
Brentford were the only team to beat City home and away last season, and the ‘three-peat’ looked on when Maupay fired them into the lead.
But Foden finally beat inspired Bees keeper Mark Flekken to haul City level before the interval.
The England midfielder headed them in front early in the second half from Kevin De Bruyne’s cross, and then completed a stylish treble to leave the visitors with their title destiny firmly in their own hands.
“I said weeks ago that Phil is having his most influence on the team,” said Guardiola.
“He’s reading the game really well, how he can play simple and be more aggressive.
“He always has the pleasure to score goals and the threat when he is close to the 18-yard box. He is an exceptional player. A short age, already more than 250 games for City. That means the influence since he arrived.
“He loves to play football and still when you see players in the street when you are a little boy he still has this sense of amateur culture. He loves to play and this season he has been so important for us.
“In terms of how he moves in small spaces. I’ve seen many really good players but the impact from Phil when he gets the ball there, he can score.
“The feeling that he can shoot or make an assist, it’s difficult to find this combination to move in the pockets and after be like a knife and be so aggressive and score goals.”
The Bees went ahead in the 21st minute with a goal straight out of the Brentford playbook.
Flekken actually claimed the assist, punting his goal kick towards Ivan Toney, who backed into Nathan Ake, easing the defender out of the flight path while letting the ball bounce past.
Maupay was left free to race clean through, coolly finishing past Ederson for his fifth goal since the turn of the year.
“We know we have a strength there with Ivan,” said boss Thomas Frank.
“We don’t do it all the time but against a team that is pressing it can be effective. Credit to Mark, Ivan and Neal, they worked it out themselves.
“It was an OK team we were facing, I must say! A good performance from us. We do a lot of things right.”