How do you refute the Jewish claim that Jesus cannot be God because Hosea 11:9 says 'I am God and not man'?

In Hosea 11:9 that was true, because Jesus had not become man yet. This takes place around the eighth century BC, and Jesus is not going to become a man until eight centuries later, so you answer it in context. Why does God say 'I am God and not man'? Without even looking it up, it is probably because man has done something dishonest and expects God to remunerate them for it, and God says, I am God, I am not man, I am not going to finagle your sin to make you feel better; I always do what is correct and righteous, because I do not sin. That is the context, dealing with the integrity of who God is and who man is, and it has nothing to do with anticipating becoming a man in the future. So the burden is on you: if something is wrong, it is because of what you did, not what God did.