How would an anarchist society stop someone from claiming your house to build a highway or a coal mine? "The self-defensive mechanisms" is just police again you just call it differently and it can do whatever it likes.
No, the self-defense mechanisms aren't the same thing as "police", since the former is structured bottom-up and the other one is top-down.
An anarchist society would be organized democratically so that the people affected by policies have a say in these decitions proportional to howeit affects them.
People with red hair would be burned, but to get to that point you have serious assumptions. That's akin to saying "what if in a Utopia, everyone decided to kill themselves for fun?" It's unrealistic and purely serves to derail the conversation against Democracy.