SUBREDDIT: r/AskReddit
TITLE: A man shoved me to the ground. A cop told me it wasn't a crime.
POST: __Background:__  I'm an 18 year old male and I'm still in high school. I was eating dinner with my mom and her boyfriend when he tried to tell me that evolution didn't exist. I told him that's just stupid. That's what I said verbatim. "That's just stupid." So as we got up to move rooms, he started shouting at me and calling me a sheep for trusting what I read in books instead of trusting what I _believe_. He had been drinking, but that didn't make it any less funny. So I laughed. And he started verbally attacking me. Calling me a delinquent kid and whatnot (I still live with my mom). So anyway, I yelled back, but before I know it, he's right in front of me shoving me on the ground. Then he offered me his phone to call the cops on him. And I took it. And he twisted my wrist until I dropped it. And I ran away and he left. I called the cops from the other room, and when the police officer showed up, I told her what went down. She basically told me that he was well within his rights to shove me since I called him stupid. Now, I get that it certainly wasn't a good idea, but I still don't understand how he's suddenly allowed to shove me, as well as threaten to beat and kill me. I was under the impression that if I wanted to I could've pressed charges. What gives?

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TL;DR: 
I got shoved and threatened during an argument, got scared, and called the cops. The officer told me that the guy who pushed me didn't do anything wrong. Why is this the case?