if you'd lived in the libertarian utopia and someone claimed to take an action for the collective good of the community wouldn't that undermine your autonomy and freedom and therefore make you valid under the NAP?
I think it matters what they are doing, if someone opposes it and they don't avoid your area or property or whatever, or can't, it would violate your NAP. If everyone agreed it would be fine.
ah... but you see OP, in a Libertarian Utopia, that wouldn't happen.
In other-words, Libertarian/Anarchist Utopia requires a Universalization of Ethics, which is simply never going to happen. Much like the New Soviet Man required to make Socialism/Communism work.