Saying installing Arch is a security risk is as similar as saying driving a manual is a safety risk.
A person's ignorance while using it is the risk, not the platform. Which is the same for any OS user. Using Ubuntu/MacOS/Windows and blindly clicking links that you dont understand doesn't then mean that Ubuntu/MacOS/Windows is a security risk. Its the user that is the security risk not understanding.
Linux Geeks doing what Linux Geeks do..