I also avoid a friend of mine. She has a 6 year old son. Or maybe he's 7. I don't know, but he's very, very sneaky and mean. When my DD was about 3, he purposely pushed her down the stairs. It was a long set of stairs that were wooden. I was standing around the corner and never knew her son was so mean or I would've been watching like a hawk. I heard DD scream and I came around that corner so fast. Dd ended up with a bloody lip and was crying pretty hard. I caught her after she rolled down about 3 steps.
My friend's other son tells her mom that he pushed my DD down the stairs on purpose, which I'm sure was true, so as discipline my friend tells him to not do that or he'd get a time out next time. He starts crying so she picks him up, cuddles him and tells him how sorry she was that she got mad at him.

My kid was the one who got hurt! I avoided them after that, but they call every so often and I have to make excuses. I'd love to explain to her why I avoid them, but I know she wouldn't believe it. She's very -how should I put it- outspoken and gets right in people's faces if they say anything or do anything she perceives as negative to her kids-even if it isn't.
One time at her house, I was there for a party, but left my kids home for obvious reasons. My nephew was swinging on a swing and this little brat was hitting him with another swing. Of course when his parents were told, they were sure he'd never do something like that.
He is just mean and it makes playdates waaaaay too hard. I am too chicken to tell his parents why I avoid them so I'm sure I come across as a real witch, but at least my kids are safe. OP, you have my sympathy and I'm sending you a

I hope things improve.