The context you are missing is that these interactions aren't limited to strangers or the internet, and typically form a pattern of regular behaviour vs just a one off comment.
A person is a victim of and suffers from the effects of their own traumatic experiences and instead of learning to deal with them and heal, they induce others to suffer some those effects as well; thus turning others into victims of that same trauma.
It's not as big and dramatic as a murder, but it's still victimization.