Leftists are not solely or distinctively responsible for exclusionary zoning and housing restriction in the US. Nationally, they're not even the biggest problem. But in many jurisdictions, places that should be the vanguards and test cases for housing reform, they are the controlling factor.
Which is why Derek Thompson addresses them so directly. What would be the point of aiming these criticisms at Republican-controlled municipalities? They don't share these values to begin with! They're not listening!
Right now, we have two parties actively propping up home values and the interests of the upper middle class. Klein and Thompson propose: what if on this issue we had two parties?