There’s a type of person who thinks that their “lived experience” trumps facts or logic. That’s why you have people who justify their racism based on a few bad experiences they had with black people or something. I try not to get in arguments with those people, because it’s a waste of time.
Thats taking the wrong lesson from things. Its completely appropriate for someone who witnessed a stabbing on public transport, to decide that talking to strangers on public transport is more dangerous than they would like. Its not racist or any -ist, its the basis for risk analysis.
You should also consider that public transport and who uses it can change immensely from one place to another. In my area, public transport is inherently risky, not to mention inconvenient, and people avoid it if at all possible.
We base our risk analysis on things that happen to us, and that’s error-prone. Just because something happened to you, that doesn’t make it a frequent occurrence. Again, just because your neighbor was a serial killer, that doesn’t mean that you have to worry about living around serial killers for the rest of your life.