A belief in nihilism is as credible as the Christian belief that Earth is 6000 years old.
Nihilism is the belief that nothing has meaning or value.
To be scientifically valid Nihilists must show that in all circumstances meaning and value does not exist. However, it is observable and testable that amongst living organisms there exists value and meaning, something that is shared by billions of human beings. The bee values its nest that it will defend with its life, nearly every mother amongst the mammals will fight to protect their young. The politician values their political office, the millionaire values their car. Even the Nihilist will value, and take meaning from, the pleasure of drawing breath after being drowned in a tub of cold water for a minute or so.
One argument that the Nihilist uses is that all value and meaning is the result of biological processes, such as hormones that drive the need to reproduce. In reply, I would say so what? Regardless of the cause, the effect exists, and thus it is valid. If the Mallard male duck is moved to mate with fifty females because of his hormones, the action of sex with lots of females has meaning and value to that individual duck, likewise as it does to the subjects of his affections.
The trouble with the Nihilist is that to validate their position they need to pretend that meaning and values do not exist across all organic life. Unfortunately for the Nihilist, their position is no different than that of the Christian who believes the Earth is 6000 years old, despite vast evidence that says otherwise.