It's kind of annoying when you hear actual 911 calls where the operator tells the person to calm down. It's like: Bro, they're about get stabbed by a psycho. How the fuck do you expect them to calm down? amirite?

They have to ask them to calm down. They need to be able to talk to the person to find out where they are and what's going on. If they encouraged emotional behavior in these situations the person would only get more upset and thus make it harder for them to get any help as well as making them even more stressed than they already are. It's expected that they'll be freaking out, they just want them to calm down so they can actually help them. If the 911 operator tells me it's okay to freak out, I'd panic even more and assume I was doomed since they weren't doing anything to help me.