It would not surprise me in the least if it was Leeds fans. There were loads last time we spanked them on the pitch - no fewer than six of them near us had left by half time of that game and they weren't the sort that cause trouble even if they weren't silent about who they supported - they bemoaned their team's weakness.
It would not surprise me if this was so-called Blue on Blue either.
Sadly this kind of incident doesn't surprise me in the least - the way I have seen some fans talk to each other, and I have been on the end of it too. Most recently my first game back from having a heart attack last autumn was the bloody 0-4 v Tottenham. There was a nasty piece of work on our row (a Johnny Come Lately from Sheffield now less) who had a habit of being always and giving Cuty players stick and abuse. He was at his worst in that Tottenham game. It was stressful to listen to especially given my health at the time. I managed to bite my tongue for 52 minutes until he abused Haaland and spewed more shite. Id had enough of the abuse and negativity towards City who were trying but just shite. I said "Why don't you go home? You're not enjoying it. " I got a volley of abuse. I said "Well, you're not a supporter. You haven't said one positive word to support the team all game." Not diplomatic i concede but the imbecile was appalling. It got worse and my Missus was concerned and I didn't engage after that but there were thinly veiled threats of somebody getting it. He was all talk and im not interested in scraping but you can see how it kicks off. It"s not just City that has this problem.