Ignoring him, is not childish. [name-calling] 'you couldn't work this out together[blaming] 'you're not strong enough to'...[put-down, criticism]

You mentioned he'd make you feel 'guilty' all over again. For sure, that's the method to his madness. Insulting you, and blaming you, are a Guilt Trip, it's manipulative. He's got a new girlfriend!! You aren't giving him, what he wants, and in an immature manner, he's trying to get you to give into his demands, by belittling you, this way.