why humans are always biased

when Man made families and gathered in communities a feeling of belonging started growing inside him and with the civilization of human life that feeling grew stronger. Man ,eversince, started positioning himself on one side against anyother side that shows hostility to his community .He shifted from caring for his personal lot in terms of food and security to caring for those around him.However , the good thing was that Man also grew some codes of conduct to control that community and built up ethics to be followed . Years passed by and Man kept and controlled his social life within the bounderies of those codes. However ,todaybecause Man occupied the totality of the planet and gathered the totality of people grouping them into allies and enemies ,he forgot about his earlier codes of conducts. He set up new codes based on no codes at all.Maybe his nostalgia to the animal life in the jungle submerged and made him break all the bonds he already created. No more family ..no more communities...no more ethics... It's simply a high tech jungle life. what drives the behaviour of Man is simply his ego .his desire to dictate not to coexist. America is the best example of this jungle.see that weird trump who overnight changes his position against the assassination of kashogji to a support to the assassin.

see how a killing of an israeli in palestine by an opressed palestinian is scandalized and the genocide daily committed by burmese on the minority in Burma is legalized.

I don't want to mention the extermination of the red indians or the exile of many subjected people here and there for no reason at all except the greed of man...
My point is when will humanity unite for a human cause no matter who is involved or where it is located...this just comes to my mind when everyday I watch the news and see killing everywhere ..wars everywhere...anger everywhere...can't we raise a new generation away from violence ...can't we omit terms of offence and rudeness from the human language register...can't we simply watch a single film scene with no 'F...' words...