Is it the business of a government or a society to dictate how people should treat one another? Where is the line to define what's OK/Not?

A big subject. The answer is NO - not in a free society. With freedom and the autonomy of self-determination comes the personal responsibility of living our lies as we see fit.  Which means if things don't work out we must look to ourselves and not place the blame om others. Look at it this way - would want people telling you how to live your life?  What to do and how to do it and what to think and believe and eat and how to spend your time and who to spend it with? Of course not. That would be totalitarianism. So you are free to live how you want and you have become responsible for yourself. Many people may not operate out of the highest and most noble of motives but they are content because they are doing what they want.  That is happiness in their eyes. 

My husband and I eat macrobiotically with the seasons but I would not force that diet on others. Some people will not come to our home just because of what we serve even when I make compromises for company! Or they may see me as morally selfish so they want nothing to do with us or any of our ways.  that is their choice and right. Many people just come from desire and habit and they eat and act how they have been taught to or have become used to.  So if they are happy with that then why should they change?  How would any government enforce eating?  Imprison people who eat fatty foods?  Take away their drivers license? Execute them?  To each his own. 

There are laws against certain types of behavior which are considered criminal.  Now when we decide to go to law, which many people do these days, they risk making a public spectacle of themselves which is why many people choose to handle such things in a more private way. But more and more laws, with their punishments if they are enforced only tend to drive people further apart than bring them together. When I was young we were taught politeness and respect and compassion and responsibility and giving back.  Which mostly though we got from watching the ways things worked in our communities. In those days there were more such things as "community standards" which were adhered to so as to avoid risking social ostracism.  In this age of lawyers seems everything is up for legal grabs with the result that people are more frightened to act for their community because they feel they will be dragged into court for overstepping their bounds. 

I just can't see the "hate" the way you seem to.  For me what you term as "hate" is nothing more than people wanting to live with what they are comfortable with. Which is mostly what they are used to. Which is natural for all of us. The hate when it comes is more likely to be a heightened resentment to some unhappiness in their lives which they keep at bay by blaming it on others.