Selfishness is a fair expectation. I would describe myself as highly selfish and hedonistic. I do that which I think will best lead me to experiencing pleasurable sensations and will best lead me away from the experience of negative sensations. That's about all that motivates (consciously) my actions.
So, if it's universal to act contrary to belief systems you either can't say someone isn't a nihilist for acting contrary to their beliefs, or you have to say to that no one is really an anything. Given you said that no one was a nihilist here, iirc, it seems you must say the same about everyone (there are no Christians, Buddhists, evolutionists, materialists, etc). Or you can just choose to be inconsistent.
So, if it's universal to act contrary to belief systems you either can't say someone isn't a nihilist for acting contrary to their beliefs, or you have to say to that no one is really an anything. Given you said that no one was a nihilist here, iirc, it seems you must say the same about everyone (there are no Christians, Buddhists, evolutionists, materialists, etc). Or you can just choose to be inconsistent.