Perhaps Haaland felt distressful after some disappointed individual performances when playing with Arsenal last season and after scoring a goal in this match, as well as some situations in the match between two team players, he wanted to take action to release his stress. But either reasons, it's very bad activity that he needs to avoid in future.
You're right because Manchester City had a tough game and almost lost to Arsenal if there wasn't a late goal in the second half. So it's clear that Haaland actions were one of those outbursts that he couldn't stand. I understand maybe Haaland got carried away and didn't think about the consequences, but the media out there will continue to highlight it as a form of reciprocity. I mean the actions and words of a player will be very sensitive given his status as a prominent player in the EPL. Hopefully, in the future he will be able to refrain from acting rashly.