You say you don't believe a person who does bad stuff can ever change, that they should be punished endlessly and they can't learn to do otherwise?

That is strange given that each of us has done bad stuff and can often feel guilty about causing hurt to others, so much so that we mend our ways and try to be better people. The refinement can start right here on Earth. You hear of criminals who have turned their lives around completely.

And this is where the confusion comes in.  Comparing what a sentient human being can and can't do whilst still alive is totally different to your claim that someone can refine themselves once dead.  For one thing, where are they going to refine themselves (I don't believe in the idea of purgatory, either)?  As far as I am aware, any such refining has to be within the context of living amongst human beings: not amongst the 'half-dead', for want of a better phrase (I'm in a hurry as I have to exit ze house in 5 minutes' time).