If I have a makefile, I can inspect it and see what it does.
If I have shell script (or indeed a makefile!) that calls `curl | bash`, I can inspect that shell script and see the URL that is used with curl, and then inspect the contents that the URL returns.
OK, I see - in theory, an attacker in control of the backend could write a handler that could craft a bash script that writes different content when `curl | bash` is used.
TBH, while I take your point, I do think it's a little disingenuous of you to claim that "You don't have the opportunity" to inspect the script prior to executing it - you ordinarily will, but can't in the unlikely event of an attack like the article describes, which would require an attacker to be in full control of the web server.
Off the top of my head, this could be mitigated in a couple of ways:
1. Hash a known-good script and check the hash matches prior to executing (this does however mean that you need to update the hash every time the remote script is changed)
2. Use curl to download the remote script to a local file first, and provide the opportunity to inspect it prior to piping it into bash
https://www.idontplaydarts.com/2016/04/detecting-curl-pipe-b...