The incident appeared to rile the Belgian, who drove City forward time and time again and eventually smashed in an unstoppable second.
City now sit 16 points clear in top spot with five games to play and could yet to break various Premier League records by the end of the season, with the 100-point mark within their sights.
"You can't take (winning the league) for granted, I've won three now but there's so many we've missed", he said.More news: OPCW continuing mission into alleged Douma gas attack despite air strikes
Goalkeeper Ederson Moraes was watching former club Benfica play Porto in the Portuguese league.
The defeat came just eight days after United momentarily halted City's title celebrations with a 3-2 come-from-behind win at the Etihad.
City's home record this season is strong, losing one and drawing one, and while United won the treble in 1999 their away record wasn't all that impressive, drawing nine and losing two from 19. It's disappointing, even more after the win last week, but this is football. "We have spent a lot of money to have these fantastic players, to make that possible".
He said: "We've got faith in one another, the players, the staff. Things have gone a bit by the wayside this year".More news: 'Night Court' actor Harry Anderson dies at home
United have Alexis Sanchez and Jesse Lingard playing in this role and Dybala is a massive upgrade on both names, at least on current form.
Arguably one of the best playmakers in the game at the moment, the 24-year-old has 21 goals and four assists in just 20 league starts this season and is the most exciting star on the show in Serie A this season.
The 2012 title win had the infamous last-gasp goal by Sergio Aguero.More news: The New Gmail Comes With Self-Destructing Emails
"If you ask me about respect, I say it is about honesty", he said. "It would be one of the best three seasons I have ever had as a player and as a manager". An inability to turn tight games into victories had blighted Guardiola's first campaign, and it would have seen them continue in the same way had they left the Vitality Stadium with only a point.