Negative stereotypes that divide people along group lines causes much misplaced hatred and, if we can overcome this type of group think, then perhaps we may obliterate most forms of discrimination, racism, and genocide.
One of the first steps in this process is the formation of "us and them" camps. People may be divided into groups due to many reasons. A major group will naturally be the citizens of individual countries, e.g. Americans, Australians, South Africans. Within countries and also across countries, people may see themselves falling into further groups, which may be due to ethnic lines and what people look like, cultural reasons, religious reasons, and more.
There is nothing wrong in having groups, and people are attracted to groups for various reasons, mainly to belong and feel part of the community. Often though, people who belong to certain groups are stereotyped, often on the basis of the behaviour of a few individuals of the group. If you begin to notice a stereotype forming, try instead to see only the individuals who are to blame for bad behaviour, and blame those people only. The stereotype isn't to blame for the actions of a few individuals, just as you personally aren't to blame if someone who looks like you or is part of your group does something wrong.
There is further danger when people of one group begin to feel they are superior to other groups based on these stereotypes, and especially when a power imbalance is in place. The group talk may state that people of a certain group, even all other people in general, are subhuman and worthless. This is a process called dehumanising. Yet, we all bleed the same, we all have feelings, we are all citizens of the world. Be aware when you begin to see a group valuing or devaluing one type of person over another type of person purely because of a group or a stereotype. It is normally illegal to do this according to the laws of most countries, because it may lead to hate speech. People are of equal value, irrespective of groups, especially as some groups can so easily be changed, e.g. when people move countries and adopt new citizenship.
Links to related articles:
International Organisation, Genocide Watch, has devised 10 steps on the road to genocide.