That you should be very careful about what you install. Cut&pasting some line from a website is the exact opposite of it. This is mostly about psychology and not technology. But there are also other issues with this, e.g. many independent failure points at different levels, no transparency, no audit chain, etc. The counter model we tried to teach people in the past is that people select a linux distribution, independently verify fingerprints of the installation media, and then only install packages from the curated a list of packages. A lot of effort went into making this safe and close the remaining issues.