Well, I don't think Wilson is a "libertarian", nor is Harry for that matter, so I'm not sure what your point is?
I also do not see Wilson being anti-British monarchy because it was a colonial empire? I doubt Wilson, as many other British people, see the British monarchy as a world oppressor...
If the libertarians are really against British monarchy and colonialism, the British's multinational corporation's economic oppression on the "Third World" nations will be end today. Have you realize that? Have you realize that western colonialism today are not ended, but only shape-shifting?
Libertarianism are part of classical-liberalism which promoting maximum liberty and advocacy for national's policy based on majority's will and interest,
including gaining more national's wealth based on any way they can. Because justice and equity for them is not always true, if anyone enforce that thing, they will call us "bias" and oppressing people's choice which different from us. That's my thought on the relevance of British royal family including Harry to the libertarianism.
Libertarianism not promoting anti-colonialism, but personal liberty. And it forbid us to forcing them to follow what is correct and wrong according to our standard. Including forcing them to obey our definition of "justice" and so-called "equity"
David Hume are the first founder of classical liberalism, he was a British philosopher
Hate to break it to you, but ALL human-beings are oppressors.
Forcing all nuclear-armed nations to launch their nukes to attack each other is the solution, so all of creatures die because of radioactive, including us. If you brave enough to see it