To me this article misses the main point for not going to mars, which is it is stupid vs the next best option of investing in building up our space infrastructure near Earth, ideally finding profitable niches (moon/asteroid mining, solar electricity? zero gravity manufacturing? I don't know what, but I am pretty sure something can be profitable up there) that support that effort so that the spend on point 1 and 2 of the article's argument is motivated by positive cash flow driving us towards whatever the feasible version of an O'Neil cylinder ends up being. Why would we ever want to go back down an expensive to escape gravity well to a barren wasteland that we would have to terraform when the opportunity to terraform more manageable chunks of space will probably exist at the same technology investment level and will almost certainly be much faster/easier/cheaper than doing a whole planet at once?