Of course, not all genocide occurs in the same way. In Rwanda, there was a long history of animosity between the Tutsi and the Hutu. The two groups were engaged in outright warfare against each other. Therefore, there was more of a basis for actual distrust, hatred, and even murder, because of ongoing bi-lateral hostilities between the groups. What really pushed the situation towards genocide in Rwanda was the use of children as soldiers. Taken while they were still very young and formative, these children were used as cannon fodder, and those that survived were frequently stripped of the ability to empathize or any of the other characteristics that most people consider human. In turn, these children became the leaders, the parents, of the new generation, and they could not teach what they themselves did not know.

Not all ethnic cleansing programs are in the form of genocide. On the contrary, horrific ethnic cleaning programs in Bosnia and other locations have heavily relied upon the use of sexual violence against non-combatant...

This is actually a very easy to explain component of ethnic cleansing programs. Almost by definition, sexual violence involves the degradation and dehumanization of the victim. In the highly-charged racist atmosphere that is present in genocidal scenarios, women in the victimized ethnic groups have already been dehumanized, making it a simple thing to victimize them.
While the misconception is that genocide occurs for no reason that is simply not true. Genocide may find its roots in struggles over natural resources, such as in Rwanda, or it may have a religious basis, as in Serbia, or be based on a country's desire to strip a group of its financial resources, like in Nazi Germany; however, there is an underlying cause for genocidal behavior. Because the dominant group does profit from such behavior, genocide is understandable. However, that does not make genocide acceptable. There are always people who stand up and refuse to participate in these scenarios, despite the fact that doing so places them in great personal danger.