My ex friend just said I'm changing?

This guy who used to be a really good friend of mine just messaged me out of the blue and said I was changing, that I now have an effed up attitude, and is saying I'm depressed and shat like that. I don't even know how to respond without saying something really rude. This past year I've matured a lot, and I've started making new friends who are way more accepting of the fact that I'd like to grow up. My ex friend is really immature (ex: he was laughing at this guy that had a speech impediment) and he can be extremely rude to me, so I cut him out of my life a while ago. How can I tell him, politely, that I'm changing for the better?