Normally I am very frugal. Key to enjoying the decline is to participate in Minimalism so that you are free from any employer and what little money you do make can go much further. So how do you rationalize renting a sports car?
The key is to realize that Minimalism does not mean "starvation." You don't want to spend so little that you never treat yourself to anything and therefore prohibit yourself from enjoying the decline. And renting a sport car, though it may seem unnecessarily frivolous, is a perfect and "must-do-once" example of treating yourself.
Understand that it IS stupid to buy a sports car. If you think about it the vast majority of your driving will fall under "errands," "work," or "transportation." You're either picking something up, going to work, or driving to a particular destination, say on "vacation." A sports car achieves all these objectives, but at an incredible price. A cheap econo-car will suffice just as well and nobody will care nor expect you to be doing such things "in style."
However, there are instances where a sports car is called for. A hot date, a high end event, a big party (wedding for example, etc.). Instances and events where, very similarly, you would wear a tux, don a suit, or get a new dress. But since these events are so rare, it is better to rent the sports car than own.
THere are other advantages to renting a sports car instead of owning. First, insurance, maintenance, is a mere fraction of what it would be if you owned it. It is very similar to what we refer to in banking as the "Three F's. - if it floats, flies, of f%cks, rent it." Technically sports cars do none of the three, but is closely related to a boat in the infrequency use is called for. Second, once you buy a sports car (say a Corvette) you are committed to that one car. YOu get to sample no others and life is too short for that. Finally, it's not like you can constantly push the sports car to its limit. One of the biggest drawbacks of the Challenger was being able to drive around 170 MPH, but effectively being forced not to because it would be foolish - cops would be pulling me over left and right.
So the next time you are at the car rental joint and the situation calls for it, upgrade to the sports car of your choice. Life is too short not to.