Never try to argue with someone who is angry, or who is in a heightened emotional state.
People do not like to be proven wrong, and will often hold onto unreasonable beliefs in order to avoid losing face. It is often best to give them room to manoeuvre rather than force them into a position they will resent.
People within groups are often most antagonistic towards those in groups that are similar to their own but different. For example a football fan is often more antagonistic to a supporter of another club than of another sport.
To make people part of a team or a group focus on a common purpose. To attack a team/group focus on different sub-groups, or types of group, and their different purposes.
Other people do not necessarily think as we do. They do not necessarily share the same values or the same criteria for judging what is right or wrong.
Whilst groups are bound by a common purpose, in order to survive they also need to be tolerant of non-conformity and differences, otherwise they won’t have to the ability to effectively evolve and adapt/react to the inevitable changing circumstances.
Something that is not able to change and adapt is more likely to fail or become extinct then similar things which can.
People who always blame others for their own mistakes or errors will continue to make them. Those that accept personal responsibility will learn from them and be less prone to making them in the future.