Carlson segment.  Carlson is basically saying exactly what you are saying in your post, i.e. Fauci is an expert in his field and economists are experts in their field.  The problem is that Fauci went on CNN and said that he didn't understand why there wasn't a federally mandated stay at home order (he was more or less baited into saying it by Anderson Cooper at th 4:10 mark of the Carlson segment).  Some, including Carlson apparently, took that as Fauci not staying in his lane and Carlson is simply pointing out that Fauci is not qualified to say whether the federal government should or should not be issuing a stay at home order as there are more considerations to such an order than simply whether it will help stop the spread of the virus.