She Just Isn't A Fighter... Right Now

Call me a bad parent but I felt the need to teach my daughter to fight. I know she has to learn as I did when I was younger but I just feel like she is gonna end up taking quite a few Ls (losses) and I can't stand by and let it happen.
She thinks the world is nice and just doesn't realize, yet, that this just isn't Mr. Roger's Neighborhood. He's deceased!
She is missing teeth and thank God it's because of age and they have fallen out and new ones are coming in. Not because of her mouth and they (teeth) have been knocked out.
She and her brother were playing in the play area of McDonald's Friday night. Initially it was just the two of them and my friend's daughter. Then a few others came in to play. And my two usually play well with anyone. Well, I hear another child- looked to be nine or ten years-old- questioning my daughter. Her voice wasn't pleasant. The girl's back was to me.
"Did you just call me a runt?" "What did you call me?" she questioned repeatedly, her voice growing louder each time.
Maurissa never said anything. She just sat at the end of the slide and looked embarrassed, scared, guilty- all of it.
"Maurissa," I called, "what are you doing?"
The girl stood over her, while holding her, I assumed, younger brother.
"Maurissa come here now!"
The girl then walked out and went to her parents.
Well, although I knew she probably was wrong and ran her mouth, I had already started getting defensive. In other words: I knew she was wrong but that little girl's folks didn't want none. My earrings were already off.
I asked her if she called the girl a name and why. She just stood there twirling the edges of her shorts. So I got unsolicited information from her younger brother. Oh, the four-year-old will tell it.
"We were runnin' and playin' and Maurissa called dat wittle white boy a runt, and his sista got mad."
I don't know why but when he said "white" I looked around, hoping no one heard him. But this is how some kids describe people.
"Okay and what were you gonna do?" I asked him. "What were you gonna do if that girl had hit your sister?"
He didn't know what to say.
"I've told yall both that you take up for each other, NO MATTER WHAT!"
I fussed the entire way home.
Once we got home, it still bothered me that she may have gotten her butt kicked. What would have happened if I wasn't there? She had to get a little tougher. She had to be prepared. Was it morally wrong to want her to learn to fight?
So when we got in the door, I started wrestling around with her. She looked confused... reasonably so. I mean I had just fussed her out and now I was laughing with her and trying to play- so she thought. I was trying to see what she had. She played around but she giggle so much that I came to my senses and realized that she was just not a fighter. Or maybe she would protect herself when she needed to and I would just have to live with that.
Or.... I could put her in karate classes.