I just read an interesting post on the navigation between realism (objectivism) and relativism/nihilism on DuckRabbit. It inspired me to offer my brief take on these issues below.
Human beings have evolved as natural systems embedded in the larger network which is the world. Our view of the world is a view from the inside. There can be no strictly objective truth as if from a standpoint outside the world. Insistence on such a standard leads to confusion. However, our participation in the world's activity provides a solid ground for knowledge and for value. We are not separate from the world, our experience is directly of the world. There is no basis for nihilism.
Also, there is no basis for extreme forms of relativism: human beings are extremely homogeneous with regard to their biology, and their position in space and time. There is therefore an underlying inter-subjective truth we share with one another. Science is based on a methodology constructed to reach this authentic intersubjective agreement. In other spheres of life, like the moral, it is much more complex and difficult, but there is no reason we can't have increasing success as our global culture evolves.