How is genocide relevant or important for philosophy?no
I am assuming that you are wondering how the existence of genocide (the fact that it has happened in the past and still happens to some degree today) is important to the overall field of philosophy. I will answer based on that assumption.
The most important connection I can make between the two is that some fields of philosophy are concerned with evil and how/why evil exists in the world. This encompasses such questions as "how can a just god allow evil to happen?"
For this field of study, the existence of genocide is clearly important. It is such a great evil that philosophers of this sort must try to account for its presence -- they must ask how and why genocide is able to exist in the world.
Philosophy serves as a manner to decide, discuss, debate, contemplate, and analyze the how and why of things. Genocide is one of those human conditions that is so barbaric that it goes against every grain of morality that exists. However, man has still engaged in it.
Many people think of philosophy as just a thought process, but from the process come certain ideas that could be used to better understand the dynamics that have lead to genocide. In this manner philosophers can help to prevent or decrease episodes of genocide among humans.