Listen don’t shoot the messenger.
The reasoning behind negative nihilism is that as one cannot prove definitively that God doesn’t exist then one cannot state as FACT that good is bad and bad is good and as a result no morals exist.I use the terms 1,0 for good and bad.
Good could be Good and Bad could be Bad.If this is true then morals would exist.
The reasoning goes that one needs to be open minded enough to accept that good and bad are different.Nihilism (+ve) can still be maintained as an alternative to negative nihilism.
At the end of the day it is only about recognising this possibility as this may affect ones overall reasoning outputs.