The only sensible thing to do is assume that it's at least possible that it was a lab leak and reevaluate the risk-benefit tradeoff of this type of research. That is a debate worth having. The rest is just posturing.
So in one sense you're right, we can only debate the likelihood of finding facts to support the theory of lab leak vs natural origin right now. The aim of this paper is to encourage that debate rather than try to silence it, the way the natural origin proponents seem to want to do.