Ex-friend trashtalking me on facebook? What to do?

[***twinkle***twinkle***]

So I was talking to this guy for a couple months since school started. I'm 18 and he's 16, we're both in high school . Anyway, he started having feelings for me. I had feelings for him but not to the degree he did. At the time, I was dating a guy. He broke up with me about a month ago. A couple weeks ago I told the guy I was talking to I kinda had feelings for him. I said the "L " word to him but I didn't mean it in a gf way, more like your my best friend/ brother thing. I was still trying to get over my ex-boyfriend at the time but he kept insisting we go out. I said I wasn't ready. Eventually, he got mad at me for crying about my ex all the time. So we stopped talking. Recently, I met another guy and we're dating now. For several days, he's been trashtalking me on fb and ig since we started dating. I only responded with a 'u mad bro ' meme on fb. I feel bad for making him upset but idk what to do about this. Any advice is appreciated thanks