That's bad advice. It's a trade-off. Installing antivirus opens some security holes and closes others. It also adds heuristic analysis. It seems to me that the security world has come to the consensus that AV is better than no AV.
Any links? If you really care about security of your OS, consider security through compartmentalization approach, which actually works. See also: https://qubes-os.org.
Security and convenience are on a spectrum. Often security works against itself by being too inconvenient, leading to human attacks as people work around the security features. If someone wants more security, it doesn't mean that they "really care about security" and want 100% bulletproof coverage. There are grey areas.
