'We' of course is not literally true, but rather to say rational opinion. I don't particularly care whether you agree on the other two, because I have a degree of logical certainty that precludes likely refutation; sort of like how I'm certain of things like non-contradiction, because if these things weren't the case then nothing would be the case.
Also don't mistake that I believe these things are at the forefront of people's mind and part of concscious, rational decision making. Most of people's motivations and decision-making is unconscious and pre-conscious, a fact that comes from the impossibility of logically analyzing all the information we encounter because our brains work so slowly. Also, for other evolutionary-biological reasons, most human beings have no problem repeating what they have heard without knowing or even thinking about it and may not be consciously aware that is what they are doing. Pointing these very things out will get you a lot of hostility, also, especially when it's rather obvious (like the Marxists who have never read a word of Marx, much less any of his predecessors or critics).