You're planning on downloading binaries and gpg keys from that site anyways. Either you trust it, in which case you might as well curl | bash, or you don't, in which case you shouldn't be running that script no matter how carefully you inspect it.
And of course you can inspect the bash script (not that it does you any good), curl > file; bash file. It's just that most people don't so that's not what is recommended .
No, you're completely wrong.
The key is available in multiple places and has been available for a while, so there is some verification that can be done.
The binary will be checked by gpg, it shouldn't matter where it's from.
Finally, if the recommmendation is to run curl foo | sh, the bash script can literally not be inspected.
The ship hasn't sailed and neither has the sites without JS one. You have made a decision to favor covenience instead of security and you're trying to make it look like it's the normal state of affairs.
Rust can be installed by downloading the appropriate package and checking it with gpg.
Recommending curling stuff to bash is ridiculous and makes a mockery of the idea of safety.