You're actually correct in how you used it, as a native English speaker, although I think "need not be" is the preferred/correct form. I think this expression is a little less common in the US compared to the UK.
>>vinay4+(OP)
"Needs not to be" and "need not be" have sharply different meanings. "Racism need not be voluntary to be racism" would have been a perfectly clear and eloquent way to make the GP's point. But that extra "s" in "needs" changes the meaning entirely, at least in American English. Are you sure that this is not also the case in the UK? I'd be very surprised.
>>neonat+NQ4
I agree that those are different, but I subconsciously read it as "need not be" and later assumed it was a mistype of that, not "needs not to be," as it's closer to the former than the latter.