I've been commuting on a bike for decades...which means riding before the sun comes up for most of the year. I don't dispute the value of a mirror, I use a mirror - but it's hardly a requirement. A mirror a tool that can enhance your situational awareness, not a crutch or a dependency, unless you have physical or mental issues a mirror can mitigate. If you need to lean on that crutch to ride, great, but please do not assume that everyone shares your handicap.
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"Let us hope our weapons are never needed --but do not forget what the common people knew when they demanded the Bill of Rights: An armed citizenry is the first defense, the best defense, and the final defense against tyranny. If guns are outlawed, only the government will have guns. Only the police, the secret police, the military, the hired servants of our rulers. Only the government -- and a few outlaws. I intend to be among the outlaws" - Edward Abbey