Is there such a forum?

[Silver]

I think most forums welcome anyone, as long as they all talk to each other civilised.

You clearly have not been to a theist forum. Most of them will ban you just for mentioning your atheism in your introduction thread.

Even if you can somehow get around to creating a thread after the introduction, you are most likely to be banned simply for debating civilly against their beliefs.

Theists on theistic forums are not known for their tolerance. They cannot and will not tolerate opposition to their beliefs. They expect atheists to swallow their crap as though it is wisdom.