I have read that thread and, frankly, apart from the known, done on purpose stuff (telemetry, remote access/disabling your car, the supercharger blocking), there are no real smoking guns or insanely crazy/unsafe things.
Is it crap engineering in many places? Sure it is. However this is pretty much what you get in any company where software isn't the main focus. Fixing bugs and rewriting legacy stinkers isn't done because it costs money and takes time from getting the new stuff (that actually will hopefully bring money) out to the market.
If you are horrified or laughing at the supposed incompetence then you have really not seen how most software is being developed, tested and deployed ... It is a wild west, despite boatloads of books being written on software engineering methodologies, new methodology du jour appearing every few years (it was extreme programming, then agile, then scrum, before we had SSADM and Prince ...). However, no matter which methodology and process you have, it always gets trumped by management decisions prioritizing other things because they don't see value in doing things properly (costs money, time, resources, nobody cares about that it will cost 10x as much money, time and resources to fix when it blows up 6 months down the road at the most inopportune moment).
And especially automotive (and embedded firmware in general), where the code is often written by some intern or the lowest bidder sub-sub-subcontractor instead of someone who actually has a clue how to write software is likely one of the places where the worst crap gets written.
This isn't new or somehow specific to Tesla - the guy explicitly named Bosch (Bosch was actually the supplier who delivered the cheating code in the original Dieselgate), but similar things were discovered elsewhere too. E.g. Toyota after the unintended acceleration fiasco:
http://www.safetyresearch.net/blog/articles/toyota-unintended-acceleration-and-big-bowl-%E2%80%9Cspaghetti%E2%80%9D-codeConsidering that stuff is actually controlling safety critical functions and that there is a heavy pressure by car makers on the regulators to allow fully "drive-by-wire" (i.e. with no mechanical connections between the steering wheel and the wheels) and autonomous cars, it should give you a pause.
There is a running joke that the IP protections, keeping everything proprietary and NDAed is not meant to protect the IP of a company but the brand in case the horrors the company products contain leak out ...