I don't know what this has to do with sports betting but yeah sports especially in high pressure situations brings the worst out in people. In the United States some cities are worse than others, but generally speaking when going to a visiting stadium it's not recommended to show your colors and gloat or talk smack when you are the minority there.
For fanatical supporters, they have a different way of supporting than ordinary supporters, they will not even hesitate to commit criminal acts if they meet opposing supporters. In my country this also happens very often, especially if it is two teams that have a very high rivalry, this will be balanced by the rivalry of the supporters too. This is indeed a very unfortunate thing to happen in football, with this bad incident indirectly tarnishing the good name of the sport itself.
Interestingly, this seems to be a tradition passed down from generation to generation, even though it has claimed many victims, they will continue to do it. There are lots of similar cases, although perhaps now bad incidents have decreased more than in the past. However, even though it is decreasing, it cannot be a justification for what a few people do. I would call this an individual, because those who act like this are a small part of the existing supporters. In fact, they are the ones who harm other supporters or even harm the team they like.
There will always be crimes, no matter what place you are in. Maybe it just highlighted Rome in this case as obviously, there are a lot of teams and fans in that city and they are really die hard fanatics and could start a fight or brawl after the game and there could be stabbing as we all know, they could be carried away with emotions and their decision is clouded and will do to protect their clubs.
Yes, this could be an isolated case and I don't think this happens very frequently. But if it did though, for sure it will garner a lot of attentions for media and portray the city as not safe. I don't think it will change as well, we just need to be very careful, not to harm anyone or protect ourselves at all times.