He should try to be reasoning in a meaningful way about infection chains and networks. Instead of using unrealistic models like one person drives to wuhan and from there it goes from one person to the next. That's not even close to how it happens because transmission varies extremely case by case. Some people are barely infectious others a super spreader. Once that point is understood one can try to assign probabilities to different scenarios or hypothesis. For example having a natural source of a virus constantly transmitting from animals to humans vs. a single event like a lab accident. Which one is more likely? How ever I'm not an expert either but  to exclude expert opinion in such cases because of some conspiracy like assumptions isn't the way to shed light on this.,(reply>), @Graham Evans fair enough. Incidents can happen for sure. However many factors have to play "perfectly" together for an outbreak. I think that speaks against the lab origin.,(reply>), @Graham Evans interesting. Single incidents/infections and no  outbreaks as far as I can see.,(reply>), I do have to withdraw the claim I made which you quoted. However this is pretty relevant : "An accident in a laboratory at the Lanzhou Veterinary Research Institute [zh] caused 65 workers to become infected with brucellosis.[65] A later report from Reuters indicates that a further 6,620 residents of Lanzhou have been infected as of November 2020, and cites the local government as saying that the outbreak was caused by polluted waste gas from a nearby biopharmaceutical factory, which was carried by wind down to the Veterinary Research Institute, where the first cases were recorded in November 2019.[66]",(reply>)," <a href=""https://en.m.wikipedia.org/wiki/List_of_laboratory_biosecurity_incidents"">https://en.m.wikipedia.org/wiki/List_of_laboratory_biosecurity_incidents</a>",(reply>), @Graham Evans mainstream in the US in non-expert circles. Self referencing BS which btw speaks lot about US mentality and education. Buy I'm sure you are different then the average US idiot and you have good sources for " lab leaks of  viruses that happen regularly and causing outbreaks" 😅