Earlier quoted context omitted.
Look at it this way: whenever you are running a program you didn't write yourself, you're running a bunch of commands you never checked. This is no different to, say, downloading a precompiled executable and running it, with all the same problems and tradeoffs.
It is different. While it is obviously true that I haven't checked all of the binaries I'm running, I at least can, through the various signatures involved, rely on the fact that it was created by a particular individual or group, whom I may trust. Would you really assign the same level of trust to, eg, a sudo(8) binary downloaded somewhere of the internet as you would to the one provided by your distribution?
Yes, you "could inspect". But this is about the instructions. And instructions to pipe curl to bash are no more or less harmful than instructions to download a binary from a "random" server and run it verbatim.
"Piping curl to bash" is a red herring. It's "running unverified code" that's the problem. Piping curl to bash just makes it viscerally obvious how dangerous that is.