Guardiola's comments followed support for Rooney from Liverpool manager Juergen Klopp, who had said on Thursday that he felt there had been an over-reaction to the episode.
Rooney had apologised after he was pictured drinking at a wedding over the weekend following England's victory over Scotland at Wembley.
"I was an international player and sometimes I drank. I was lucky there were no pictures. We are people and are old enough to take responsibility. But it's private life," Guardiola told reporters on Friday.
"I don't like it when people comment on my private life so I won't comment. I have a lot of respect for the career of Wayne Rooney."
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Guardiola also said he was relieved that his City players had returned unscathed from international duty and hinted he might ring the changes for Saturday's Premier League clash at Crystal Palace.
"The players who played 90 minutes are tired, especially the South Americans. But they are fit and that is the most important thing," he added.
"There are 23 in the squad who all need to play. They need time, they are human beings. The calendar is so stressful for the players. I rest but the players don't. It's so demanding. They cannot lose, they cannot play bad."
City, who are third in the table, face 16th-placed Palace on Saturday having won just once in the last five league games with three draws and a defeat, including 1-1 home draws against Everton, Southampton and Middlesbrough.
"We didn't win three games at home and we lost six points. But I try to be optimistic. We deserved to win and I have a lot of confidence in my team," Guardiola said.
"We created enough to win the games and concede few. But we need to improve to find the right way to win these kinds of matches."
(Reporting by Shravanth Vijayakumar in Bengaluru; Editing by Ian Chadband)
