Because when someone uses a symbol while they do something shitty, they are associating that symbol with their shitty behaviors. Human brains are wired to identify paterns and associations for threat identification. That’s why cops all dress differently than EMT’s.

If your ex-girlfriend left you in a nasty break up, you might avoid her favorite restaurant, cry when you hear her favorite songs, or even get upset just seeing a similar car to the one she drove. You cant drown out a dog whistel, all you can do is point it out.