Is Not wanting to Talk About it, an answer?

I, seriously, never knew that if you didn't want to discuss something...like something you did or said that was controversial, you could just say I don't want to talk about it. This is an answer? I thought it was a non-answer especially after I was accused of something. Example;

Person 1, a close friend: "You are so dumb."

Me:  "What do you mean?"

Person 1: "You know. I'm not going to tell you. You know."

Me: "But can you be more specific? What have I done that was, in your opnion, dumb?"

Person 1:    "You know.  I don't want to talk about it."

Me: "Wait, what? Can't I know waht you mean?"

Person 1: "I told you I don't want to discuss this."

Me: "So, that's it? Why can't you tell me what you mean?"

Person 1: Walks away.

Me, two days later after not hearing from Person 1...in a text: "Hi.  Can you now tell me what you mean? How am I dumb? Did I say something that upset you? What?"

Person 1:  no reply.

Me, three days later in an email. "I thought we were friends and we could talk about anything. What happened? You're killing me."

Me on Facebook: "Apparently, asking a friend for an explanation about something I did is not allowed.  You do something, apparently but don't know you did it or said something that made a person lash out, and you ask for an explanation but that's not allowed.  I know, a person doesn't have to do what you would like, or you hope they would do. Some people don't have empathy; can not put themselves in the shoes of the person who is hurting from the silence from not knowing. But live goes on."

One week later, Person 1, who is not on Facebook emailed me: "You asked me for reasons why I said you are dumb and I tell you I don't want to tell you, you know why I said that. But this has gotten even worst. You post on Facebook that you don't think I have empathy and you won't accept my answer. I don't want to talk about it...that's my answer.  We run into each other since we travel in the same circles so I hope we can be coordial.  This conversation is over."

Me ugly crying from being ignored for weeks; not understanding why she said what she said and then getting reduced to just someone in our circle with whom I am just to be coordial with, not a friend, not anyone of great importance or someone to share anything with....albeit, maybe the weather.  She doesn't have to explain herself but I'm left to be sad and blindsided. And the fact that she doesn't care that I'm hurting over losing her friendship...just kills me. 

I had to no idea you could do this. Break someone's heart and just move on.  No one ever told me that that is acceptable... to say you don't want to discuss something. Where have I been?