Having lots of money earned does not make a person bad.

They never said that. So maybe you're disagreeing with their reasoning because you don't know what it is.

They say billionaires are bad because they have a lot of money and don't use it to help people. This isn't even talking about billionaire who engage in actually/actively morally wrong deeds to acquire money.

If you produce a product so excellent that consumers give you 1 billion dollars ($1.000.000.000) in pure profit, there would be no problem if you kept a nest egg to ensure your livelihood and then used the rest to provide aid where it's needed. You would still be a bad person for sitting on it, instead of spreading it to help people that aren't well off. A person can live very well on $300K pretty much anywhere in the world: that means $999,700,000 is not materially improving your life and you are hoarding it for no good reason.