Why even have nihilism

If you cant be purely nihilist or purely relativist do those things even exist. Saying your beliefs are nihilist would be like saying, "look at that bright nothing". Why would someone even try to explain their thoughts? I could understand if someone thought that morals were just made up by humans, but did exist because people believe in them. Would a nihilist not care if or seek reprisal if someone killed one of their relatives or friends?

I personally think that morals exist solely because humans have thought of them. Some morals should be considered absolute and some relative to the culture that holds them. For example, pedophilia, rape, murder, torture no matter the culture bring unwanted physical pain to the victim no matter what culture they come from, hence they are absolute. However, political ideology, educational goals and even the idea of success change from culture to culture. These things have proven to have differing levels of success for different people, thus they are relative.

If I say that my opinion is the only truth is that absolutist, even though I incorporate relative thoughts in my opinion?