The modern recognition of the value and autonomy of the human individual has unfortunately obscured the obligation that the individual still has to others. For it is still in each other -- together -- that we find happiness, meaning, and security, if we find them at all.
Why the first rule? If there is no harm, how could it be immoral? It isn't increasing any suffering. The second rule(aka platinum rule) is to help prioritize empathy when thinking about harm. Other people experience things differently, and they may not like the same things.
Contemporary research into moral reasoning suggests that, to do otherwise, would be counter-productive at best, and at worst can serve to entrench the harmful beliefs further.
We are so divided and negative towards each other. We see each other as obstacles - as a another opinion to be eradicated. Sometimes, just accepting the differences in others, will cause them to show you the same respect.
This goes beyond slavery. This would include manipulation as well. To rob a person of his/her free will is the same as robbing him/her of his/her humanity.
Understand that the events of one's life shapes their perception of the world. While you might not share a point of view, their opinions are inevitably the result of the sum of their experiences.
Speech is more than the ability to convey thoughts through a sequence of sounds. Persons in dialogue collaboratively create new ideas. Lifetimes of disparate experiences are brought to bear on a particular topic, improving each participant.
To be human is to be able to satisfy primitive needs and desires through complex and counter-intuitive strategies, particularly, foregoing short term benefits to work together for a long term goal.
Biases in perception, probability estimation, and ethical decision-making all threaten our ability to make choices consistent with our values. For example, the availability heuristic combines with omission bias to fuel the anti-vaccination movement.
Empirical evidence guides rational thought. The universe is a wondrous and changing place and there is much we don't know. Only by seeking evidence and being willing to incorporate what we discover will we advance our collective knowledge.