This site's argument is that the software publisher can selectively attack users during a live software install, in a way that they don't stand a chance of detecting by inspection (or of having proof of after the fact).
1) Distributing software via bash script is a bad idea
2) Sensible people review the bash scripts they downloaded before running them
3) But haha! Here is a clever trick that evades that review.
And I'm not persuaded by 3) being interesting because I already rejected 1) and 2), and I consider 3) to just be proving my point -- you (for all you!) are not competent to perform a very brief but somehow thorough security review of a shell script that probably has further dependencies you aren't even looking at, and the actual reasoning to apply when deciding to install software this or any way is purely "Do I trust the entity I have this TLS connection open with to run code on my machine?".