This stupid canard again. If you want to install software on your system, the installer has to be run as root. If you dont want to actually install calibre, then simply run the installer as a normal user and do an isolated install, which does not require root, instructions for which are further down the page, which this idiot seems to not have bothered to read.
Someone needs to write an article on 10 dumb mistakes security "experts" make when giving sysadmins advice.