An incumbent power feeling threatened by a rising power is a very dangerous situation, and pushing polarizing narratives escalates the danger.
The fact is, if it did come from a lab, what difference would it make? Everybody does gain-of-function research. Everybody has lab accidents. The only reason why anybody is pushing this idea is as a geopolitical stalking horse designed to make China seem like a legitimate target for agression.
For the record, I'm not a big fan of China - but I think deteriorating relations between the US and China open the door to the possibility of war, which is a prospect that is so horrible coronavirus totally pales in comparison. People carelessly fanning tensions to pursue their own limited domestic political objectives has led to devastating wars before, and I don't think sane adults should amplify these people's narratives.