I have written more than enough about the oath of allegiance to Queen that would-be Canadian citizens have to take, but I have thought of an analogy that I like and which just might help us think the matter through. The Canadian citizenship is like marriage ― not necessarily in some romantic or esoteric way, though there is perhaps that too ― but in that it is a legal status into which anyone who fulfills some conditions prescribed by law is entitled to enter upon making a solemn, public statement before an official. For citizenship, the statement in question is the oath of allegiance. For marriage, it is the exchange of vows. The text of both the oath and the vows (for civil marriage) is prescribed by statute.
So let’s assume that the vows prescribed for civil marriage include a promise of fidelity, as the vows prescribed for religious marriages do. And imagine a couple of swingers who want to get married ― but keep their swinging lifestyle. The state tells them they must promise to be faithful to each other ― otherwise, no marriage. Would they be justified in challenging the constitutionality of the vows the state imposes on them, arguing that they could not in good conscience keep their preferred lifestyle after making such vows? (I am assuming that swinging in itself would be constitutionally protected by the liberty guarantee of s. 7 of the Charter ― just as “loitering” is: see R. v. Heywood,  3 S.C.R. 761.) Some might say that the vows of fidelity, properly understood, do not preclude a swinging lifestyle with the consent of the other spouse. But, as I explained yesterday, the Supreme Court has held that courts must respect people’s understandings of their conscientious duties. That holding, in Syndicat Northcrest v. Amselem, 2004 SCC 47,  2 S.C.R. 551, was in a religious context, but I’m not sure that there ought to be a difference here. What we are talking about is a solemn vow, not just a business contract (for which a court can impose its own interpretation on a party). I, for one, would be inclined to think that the such a constitutional challenge should succeed.
Now as it happens, the solemn statement required of a party to a civil marriage in a Canadian province contains no promise of fidelity or indeed any other vow. (Ontario’s, which seems fairly typical of common law provinces, only says “I do solemnly declare that I do not know of any lawful impediment why I, AB, may not be joined in matrimony to CD.”) I know very little about family law, so I have no idea whether there is a particular reason why, unlike the religious vows, this statement does not contain any promises, but perhaps this is for the reason I am trying to get at with my analogy: the state should not extract any promises from citizens, beyond of course a standing undertaking to keep the law. Since there is no law against swinging or adultery (and if there were, such a law would surely be unconstitutional), the state would not be justified in demanding that people forbear from it as a condition for acquiring a status that is otherwise open to them.
I think it is the same for citizenship. Since not feeling “true allegiance” to the monarchy is not against the law, the state should not be imposing it as a condition for acquiring it. Whether or not you like swingers and republicans, there are things you ought not to be demanding of them.