The person you replied to is right, the "security" of Linux might as well be nonexistent compared to macOS and especially iOS/Android. Even the developers of Secureblue (https://secureblue.dev/) state that despite their hardening and mitigations Linux still lags far behind macOS (and possibly Windows) security-wise. The only Linux derivative that has proper security is Android, and even better GrapheneOS.

https://privsec.dev/posts/linux/linux-insecurities/

https://madaidans-insecurities.github.io/linux.html

I also commented here on Linux phones, the same can apply to Linux as a desktop OS: https://news.ycombinator.com/item?id=46997397

Also on top of that Linux/Windows laptops also lack the hardware-backed security that Macs and to an extent some Chromebooks have.

Linux is easier to misconfigure. Macs resists being misconfigured insecurely. At their tightest, I'd say neither is fundamentally more insecure than the other. (The exception would be M5-based Macs, which come with MIE. Though that isn't a macOS vs Linux thing per se.)

Security by obscurity worked quite well