But where is that "free speech and open discussion" supposed to take place?
Every conversation takes place somewhere, on someone's turf, not on some neutral no-man's land.

The rule of the turf takes precedence: the one who owns the turf where the conversation takes place has the say.

What is the use of such speculations?

In a forum discussion long ago, someone proposed to have solved this problem by pointing out that ethics was originally a part of aesthetics, and that it was aesthetics that dictates what is ethical.
How do you feel about this?

This reasoning is tailored after Christian theism. But there are other theisms apart from Christianity (and other Abrahamic religions), for example in Hinduism. In those other theisms, atheism is conceived of differently than in Christianity, and the requirements put forward in favor of theism are different.

In discussions of God and atheism, why give supremacy to Christianity, as if it would have monopoly over theism and all things related to it?

Nope.

"I think if you asked, most parents would say they want their children to be happy, rather than wealthy, recognised, popular or influential."

But what do those parents mean by "happy"?
It seems to me they mean exactly 'wealthy, recognised, popular or influential', they just don't spell it out like this.
How can a person be happy, without also being wealthy, recognised, popular or influential? It's not clear how such is possible.