> They may have to explain their position though, in the same way as anyone else.

Exactly. An explanation is not the same as meeting a burden of proof. Discussion is not debate.

Explanation of one's opinion on either side is an informative process, not an investigative one. It is not intended to "prove."

Where proof either way is impossible, the idea of "burden of proof" becomes meaningless.

So while debating certain topics is pointless and inconclusive, discussion may be fruitful in other ways.