Why are people so very strange and terrible to each other?

cause everyone is different and some people are mean

Because most have nothing else in their life.

People who are feeling confident and secure and have self respect don't feel a need to call people names, criticise, bully, shout, etc. 

So often people feel a need to build false confidence by trying to get people to fear them. The important thing for them is to be noticed, at whatever cost. 

It is just human nature.  Some people build themselves up by cutting other people.  Most do not want to be judged by others standards.  Unique people usually do not judge cause they are being judged by the small people.  They can usually stand tall regardless of what other people say or do.  It is the little people who place judgment on others.  Usually to make themselves look better.  Some just like cutting other down.

I ain’t sure exactly what situation. But I have found that people can be totally unethical and wrong. I have seen people criticise whether it is racial or sometimes it’s not even about that, it’s from the same people or same nationality. I have had so called friends of the family, or so called relatives that seem to like hating on me. 

They never ask themselves this question and I always think, Why are you here then?! I didn’t ask you to come here. I didn’t ask you to come our house. I didn’t ask you to visit. People like many people, wherever you see them or meet them, they have no shame!