I called the guy Im seeing a pervert on a text message and he is filing a slander suit & restraining order?

Can he do this and if he does can I fight it? I WAS seeing him and he told me he wasn't sleeping with anyone and I found out he was sleeping with a girl in front of a 5 year old kid. I called one of his ex 's to see if he always had this kind of behavior and now he is filing a slander suit and a restraining order. What should I do legally? I told him I was done with him because my doctor said she thought his behavior around kids in unhealthy and he wants to file a slander suit against her to.