Genocide is always a problem, wherever it may occur. Often in world history, the international community turns a blind eye to genocide if it happens in Africa. Almost as if there is an assumption that Africans are supposed to slaughter each other, and therefore it is less of a crime against humanity. Maddening.
The long range problems associated with Rwanda's example are that many of the best and brightest in government, education and engineering were killed off, denying that country all of their collective potential. Secondly, it contributes to a dreadful cycle of revenge killing that could lead to future genocides.
The only real justification for the genocide was the idea that the Tutsi had historically oppressed the Hutu. I believe it was also alleged that the Tutsi had had something to do with the death of the Rwandan president. So this is not all that different from the reasons for the Holocaust -- one group had supposedly been harming the other.
The genocide that is going on in Rwanda has been compared the genocide that happened during WW2. I couldn't give you actual figures but the number of people who have already been killed and the many more who have been dispaced from their homes as a result of political upheaval is more than noteworthy and certainly going largely unreported. Add to this the fact that it has been going on since the early 90s. There are obviously those who believe that any time innocent people are being killed and the world at large is doing nothing about it, that in itself is a crime. Ignoring it, therefore, is the same thing as justifying it.
I see you are a teacher. It might be of interest to you to look into some free publications by the Holocaust Museum. I received some DVDs in the mail a few years ago and am not sure if they are still available, but even now there are several reports, productions and educational materials (suitable for a HS classroom) available by following the link below.