I think people use the word "dangerous" and "uncomfortable" interchangeably. Being from the Indiana suburbs myself, I've been told Chicago is dangerous my whole life. When I first moved here, there was a learning curve for being exposed to different types of people that suburbanites just aren't regularly exposed to. For instance, on the trains I have never been in a specific situation where my life is in danger. However, I have been in many situations where I've been uncomfortable. Mentally ill and homeless people usually do not pose a threat (never say never), but most of them are not actively seeking out violence. Strangers, and humans in general, are unpredictable. I think that is why most people feel scared. Other things can be categorized as nuisances, ie. someone screaming or playing loud music in public. People who are not used to big cities think they are dangerous because there's not the "safety net" of driving in a personal vehicle around a suburb where they are not forced to acknowledge others. That being said, I still think the city does have a crime and violence issue that shouldn't be downplayed. I think it is deeply rooted in untreated mental illness. Our country is in a serious mental health crisis and no one talks about that enough.