I just calls 'em as I sees 'em. And on this one, I will defend you. On its face, the argument being ridiculed is quite plausible: The USPS delivers tons of junk mail, which is bad for the environment, so killing the service would be an environmental good. (I have a PO Box in which I receive about 90% junk mail, with no apparent way to stem the flood.)
Now, that argument might well be wrong, for a number of reason. For instance, it might be that in the absence of the USPS, FedEx would deliver the junk mail instead. Or perhaps the USPS does so much good otherwise that the environmental bad is more than offset. But Clarissa does not offer any such reason as to why the "Libertarian" argument is wrong. (Apparently, it is a vague, nameless "Libertarian" mass that offers the argument, as there is no link to anyone actually offering it.) Her "counter-argument" is nothing but sneering: as if any libertarian ever had any actual concern about the environment!
This rubbish is on about the same level of "argument" as "John Maynard Keynes loved the Nazis!"