In Man City news, Cityzens held on with 10 men in the second half to win 2-0 and maintain their 100% start to the Premier League, but Guardiola felt Taylor had lost control of the game before Rodri's red card.
The Spain midfielder was dismissed for violent conduct after grabbing Morgan Gibbs-White around the throat at the start of the second half, and faces a three-match ban that rules him out of City's crucial clash at title rivals Arsenal on 8 October.
As well as dismissing Rodri, Taylor booked 10 other players – seven from Forest – and also showed a yellow card to Guardiola.
"The game was incredibly perfect for 35 minutes for both sides but after that, when it became chaos, it was not our responsibility, that is for sure," Guardiola said.
"With all the yellow cards, the responsibility is not Nottingham Forest or City's that's for sure. The referee has changed the game, absolutely."
In other Man City news, Guardiola said Rodri had apologised to his team-mates for his red card, which will also see him miss league games at Wolves on 30 September and at home to Brighton on 21 October, and compared the incident to Kyle Walker's dismissal in Champions League against RB Leipzig in the 2021-22 season.
"Hopefully Rodri will learn," Guardiola added. "He had to control himself and his emotions. I can get a yellow card, but Rodri can't. I don't play – the guys who do have to be careful.
"Kyle has done this in the past – they know they shouldn't do it – but it is emotions. Whatever happens, you have to control yourself. I am angry, because I don't like playing with 10 men.
"I said to the players at half-time to be careful because of what had happened in the last 10 minutes [of the first half] but we fell into the trap."