When an atheist makes a claim against a theist, e.g. "your God is evil," they are claiming that the theist's idea of a God is the idea of an evil God. They may often back this up with Bible verses, where God supports genocide, rape, oppression, etc. I've done this against theists, and they don't usually have a good response.
Now, to your other point. It's impossible to prove something doesn't exsist; I have never seen a unicorn myself, or even evidence of a unicorn, therefore I don't believe in unicorns, and will say that your claim of unicorns is false. Unless you show me evidence, I'm not going to believe that unicorns exsist. I will feel free to call bullshit on your unicorn delusion.
Now, to your other point. It's impossible to prove something doesn't exsist; I have never seen a unicorn myself, or even evidence of a unicorn, therefore I don't believe in unicorns, and will say that your claim of unicorns is false. Unless you show me evidence, I'm not going to believe that unicorns exsist. I will feel free to call bullshit on your unicorn delusion.
Gone